Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

26 files changed, 19659 insertions, 0 deletions

diff --git a/js/src/debugger/DebugAPI-inl.h b/js/src/debugger/DebugAPI-inl.h
new file mode 100644
index 0000000000..bbd6714247
--- /dev/null
+++ b/js/src/debugger/DebugAPI-inl.h
@@ -0,0 +1,180 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_DebugAPI_inl_h
+#define debugger_DebugAPI_inl_h
+
+#include "debugger/DebugAPI.h"
+
+#include "vm/GeneratorObject.h"
+#include "vm/PromiseObject.h"  // js::PromiseObject
+
+#include "vm/Stack-inl.h"
+
+namespace js {
+
+/* static */
+bool DebugAPI::stepModeEnabled(JSScript* script) {
+  return script->hasDebugScript() && stepModeEnabledSlow(script);
+}
+
+/* static */
+bool DebugAPI::hasBreakpointsAt(JSScript* script, jsbytecode* pc) {
+  return script->hasDebugScript() && hasBreakpointsAtSlow(script, pc);
+}
+
+/* static */
+bool DebugAPI::hasAnyBreakpointsOrStepMode(JSScript* script) {
+  return script->hasDebugScript();
+}
+
+/* static */
+void DebugAPI::onNewGlobalObject(JSContext* cx, Handle<GlobalObject*> global) {
+  MOZ_ASSERT(!global->realm()->firedOnNewGlobalObject);
+#ifdef DEBUG
+  global->realm()->firedOnNewGlobalObject = true;
+#endif
+  if (!cx->runtime()->onNewGlobalObjectWatchers().isEmpty()) {
+    slowPathOnNewGlobalObject(cx, global);
+  }
+}
+
+/* static */
+void DebugAPI::notifyParticipatesInGC(GlobalObject* global,
+                                      uint64_t majorGCNumber) {
+  Realm::DebuggerVector& dbgs = global->getDebuggers();
+  if (!dbgs.empty()) {
+    slowPathNotifyParticipatesInGC(majorGCNumber, dbgs);
+  }
+}
+
+/* static */
+bool DebugAPI::onLogAllocationSite(JSContext* cx, JSObject* obj,
+                                   HandleSavedFrame frame,
+                                   mozilla::TimeStamp when) {
+  Realm::DebuggerVector& dbgs = cx->global()->getDebuggers();
+  if (dbgs.empty()) {
+    return true;
+  }
+  RootedObject hobj(cx, obj);
+  return slowPathOnLogAllocationSite(cx, hobj, frame, when, dbgs);
+}
+
+/* static */
+bool DebugAPI::onLeaveFrame(JSContext* cx, AbstractFramePtr frame,
+                            jsbytecode* pc, bool ok) {
+  MOZ_ASSERT_IF(frame.isInterpreterFrame(),
+                frame.asInterpreterFrame() == cx->interpreterFrame());
+  MOZ_ASSERT_IF(frame.hasScript() && frame.script()->isDebuggee(),
+                frame.isDebuggee());
+  /* Traps must be cleared from eval frames, see slowPathOnLeaveFrame. */
+  mozilla::DebugOnly<bool> evalTraps =
+      frame.isEvalFrame() && frame.script()->hasDebugScript();
+  MOZ_ASSERT_IF(evalTraps, frame.isDebuggee());
+  if (frame.isDebuggee()) {
+    ok = slowPathOnLeaveFrame(cx, frame, pc, ok);
+  }
+  MOZ_ASSERT(!inFrameMaps(frame));
+  return ok;
+}
+
+/* static */
+bool DebugAPI::onNewGenerator(JSContext* cx, AbstractFramePtr frame,
+                              Handle<AbstractGeneratorObject*> genObj) {
+  if (frame.isDebuggee()) {
+    return slowPathOnNewGenerator(cx, frame, genObj);
+  }
+  return true;
+}
+
+/* static */
+bool DebugAPI::checkNoExecute(JSContext* cx, HandleScript script) {
+  if (!cx->realm()->isDebuggee() || !cx->noExecuteDebuggerTop) {
+    return true;
+  }
+  return slowPathCheckNoExecute(cx, script);
+}
+
+/* static */
+bool DebugAPI::onEnterFrame(JSContext* cx, AbstractFramePtr frame) {
+  MOZ_ASSERT_IF(frame.hasScript() && frame.script()->isDebuggee(),
+                frame.isDebuggee());
+  if (MOZ_UNLIKELY(frame.isDebuggee())) {
+    return slowPathOnEnterFrame(cx, frame);
+  }
+  return true;
+}
+
+/* static */
+bool DebugAPI::onResumeFrame(JSContext* cx, AbstractFramePtr frame) {
+  MOZ_ASSERT_IF(frame.hasScript() && frame.script()->isDebuggee(),
+                frame.isDebuggee());
+  if (MOZ_UNLIKELY(frame.isDebuggee())) {
+    return slowPathOnResumeFrame(cx, frame);
+  }
+  return true;
+}
+
+/* static */
+NativeResumeMode DebugAPI::onNativeCall(JSContext* cx, const CallArgs& args,
+                                        CallReason reason) {
+  if (MOZ_UNLIKELY(cx->realm()->isDebuggee())) {
+    return slowPathOnNativeCall(cx, args, reason);
+  }
+
+  return NativeResumeMode::Continue;
+}
+
+/* static */
+bool DebugAPI::onDebuggerStatement(JSContext* cx, AbstractFramePtr frame) {
+  if (MOZ_UNLIKELY(cx->realm()->isDebuggee())) {
+    return slowPathOnDebuggerStatement(cx, frame);
+  }
+
+  return true;
+}
+
+/* static */
+bool DebugAPI::onExceptionUnwind(JSContext* cx, AbstractFramePtr frame) {
+  if (MOZ_UNLIKELY(cx->realm()->isDebuggee())) {
+    return slowPathOnExceptionUnwind(cx, frame);
+  }
+  return true;
+}
+
+/* static */
+void DebugAPI::onNewWasmInstance(JSContext* cx,
+                                 Handle<WasmInstanceObject*> wasmInstance) {
+  if (cx->realm()->isDebuggee()) {
+    slowPathOnNewWasmInstance(cx, wasmInstance);
+  }
+}
+
+/* static */
+void DebugAPI::onNewPromise(JSContext* cx, Handle<PromiseObject*> promise) {
+  if (MOZ_UNLIKELY(cx->realm()->isDebuggee())) {
+    slowPathOnNewPromise(cx, promise);
+  }
+}
+
+/* static */
+void DebugAPI::onPromiseSettled(JSContext* cx, Handle<PromiseObject*> promise) {
+  if (MOZ_UNLIKELY(promise->realm()->isDebuggee())) {
+    slowPathOnPromiseSettled(cx, promise);
+  }
+}
+
+/* static */
+void DebugAPI::traceGeneratorFrame(JSTracer* tracer,
+                                   AbstractGeneratorObject* generator) {
+  if (MOZ_UNLIKELY(generator->realm()->isDebuggee())) {
+    slowPathTraceGeneratorFrame(tracer, generator);
+  }
+}
+
+}  // namespace js
+
+#endif /* debugger_DebugAPI_inl_h */
diff --git a/js/src/debugger/DebugAPI.h b/js/src/debugger/DebugAPI.h
new file mode 100644
index 0000000000..26cdfe9056
--- /dev/null
+++ b/js/src/debugger/DebugAPI.h
@@ -0,0 +1,415 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_DebugAPI_h
+#define debugger_DebugAPI_h
+
+#include "vm/GlobalObject.h"
+#include "vm/Interpreter.h"
+#include "vm/JSContext.h"
+#include "vm/Realm.h"
+
+namespace js {
+
+// This file contains the API which SpiderMonkey should use to interact with any
+// active Debuggers.
+
+class AbstractGeneratorObject;
+class PromiseObject;
+
+/**
+ * DebugAPI::onNativeCall allows the debugger to call callbacks just before
+ * some native functions are to be executed. It also allows the hooks
+ * themselves to affect the result of the call. This enum represents the
+ * various affects that DebugAPI::onNativeCall may perform.
+ */
+enum class NativeResumeMode {
+  /**
+   * If the debugger hook did not return a value to manipulate the result of
+   * the native call, execution can continue unchanged.
+   *
+   * Continue indicates that the native function should execute normally.
+   */
+  Continue,
+
+  /**
+   * If the debugger hook returned an explicit return value that is meant to
+   * take the place of the native call's result, execution of the native
+   * function needs to be skipped in favor of the explicit result.
+   *
+   * Override indicates that the native function should be skipped and that
+   * the debugger has already stored the return value into the CallArgs.
+   */
+  Override,
+
+  /**
+   * If the debugger hook returns an explicit termination or an explicit
+   * thrown exception, execution of the native function needs to be skipped
+   * in favor of handling the error condition.
+   *
+   * Abort indicates that the native function should be skipped and that
+   * execution should be terminated. The debugger may or may not have set a
+   * pending exception.
+   */
+  Abort,
+};
+
+class DebugScript;
+class DebuggerVector;
+
+class DebugAPI {
+ public:
+  friend class Debugger;
+
+  /*** Methods for interaction with the GC. ***********************************/
+
+  /*
+   * Trace (inferred) owning edges from stack frames to Debugger.Frames, as part
+   * of root marking.
+   *
+   * Even if a Debugger.Frame for a live stack frame is entirely unreachable
+   * from JS, if it has onStep or onPop hooks set, then collecting it would have
+   * observable side effects - namely, the hooks would fail to run. The effect
+   * is the same as if the stack frame held an owning edge to its
+   * Debugger.Frame.
+   *
+   * Debugger.Frames must also be retained if the Debugger to which they belong
+   * is reachable, even if they have no hooks set, but we handle that elsewhere;
+   * this function is only concerned with the inferred roots from stack frames
+   * to Debugger.Frames that have hooks set.
+   */
+  static void traceFramesWithLiveHooks(JSTracer* tracer);
+
+  /*
+   * Trace (inferred) owning edges from generator objects to Debugger.Frames.
+   *
+   * Even if a Debugger.Frame for a live suspended generator object is entirely
+   * unreachable from JS, if it has onStep or onPop hooks set, then collecting
+   * it would have observable side effects - namely, the hooks would fail to run
+   * if the generator is resumed. The effect is the same as if the generator
+   * object held an owning edge to its Debugger.Frame.
+   */
+  static inline void traceGeneratorFrame(JSTracer* tracer,
+                                         AbstractGeneratorObject* generator);
+
+  // Trace cross compartment edges in all debuggers relevant to the current GC.
+  static void traceCrossCompartmentEdges(JSTracer* tracer);
+
+  // Trace all debugger-owned GC things unconditionally, during a moving GC.
+  static void traceAllForMovingGC(JSTracer* trc);
+
+  // Trace debugging information for a JSScript.
+  static void traceDebugScript(JSTracer* trc, JSScript* script);
+
+  static void traceFromRealm(JSTracer* trc, Realm* realm);
+
+  // The garbage collector calls this after everything has been marked, but
+  // before anything has been finalized. We use this to clear Debugger /
+  // debuggee edges at a point where the parties concerned are all still
+  // initialized.
+  static void sweepAll(JSFreeOp* fop);
+
+  // Add sweep group edges due to the presence of any debuggers.
+  static MOZ_MUST_USE bool findSweepGroupEdges(JSRuntime* rt);
+
+  // Destroy the debugging information associated with a script.
+  static void destroyDebugScript(JSFreeOp* fop, JSScript* script);
+
+  // Validate the debugging information in a script after a moving GC>
+#ifdef JSGC_HASH_TABLE_CHECKS
+  static void checkDebugScriptAfterMovingGC(DebugScript* ds);
+#endif
+
+#ifdef DEBUG
+  static bool edgeIsInDebuggerWeakmap(JSRuntime* rt, JSObject* src,
+                                      JS::GCCellPtr dst);
+#endif
+
+  /*** Methods for querying script breakpoint state. **************************/
+
+  // Query information about whether any debuggers are observing a script.
+  static inline bool stepModeEnabled(JSScript* script);
+  static inline bool hasBreakpointsAt(JSScript* script, jsbytecode* pc);
+  static inline bool hasAnyBreakpointsOrStepMode(JSScript* script);
+
+  /*** Methods for interacting with the JITs. *********************************/
+
+  // Update Debugger frames when an interpreter frame is replaced with a
+  // baseline frame.
+  static MOZ_MUST_USE bool handleBaselineOsr(JSContext* cx,
+                                             InterpreterFrame* from,
+                                             jit::BaselineFrame* to);
+
+  // Update Debugger frames when an Ion frame bails out and is replaced with a
+  // baseline frame.
+  static MOZ_MUST_USE bool handleIonBailout(JSContext* cx,
+                                            jit::RematerializedFrame* from,
+                                            jit::BaselineFrame* to);
+
+  // Detach any Debugger frames from an Ion frame after an error occurred while
+  // it bailed out.
+  static void handleUnrecoverableIonBailoutError(
+      JSContext* cx, jit::RematerializedFrame* frame);
+
+  // When doing on-stack-replacement of a debuggee interpreter frame with a
+  // baseline frame, ensure that the resulting frame can be observed by the
+  // debugger.
+  static MOZ_MUST_USE bool ensureExecutionObservabilityOfOsrFrame(
+      JSContext* cx, AbstractFramePtr osrSourceFrame);
+
+  // Describes a set of scripts or frames whose execution observability can
+  // change due to debugger activity.
+  class ExecutionObservableSet {
+   public:
+    using ZoneRange = HashSet<Zone*>::Range;
+
+    virtual Zone* singleZone() const { return nullptr; }
+    virtual JSScript* singleScriptForZoneInvalidation() const {
+      return nullptr;
+    }
+    virtual const HashSet<Zone*>* zones() const { return nullptr; }
+
+    virtual bool shouldRecompileOrInvalidate(JSScript* script) const = 0;
+    virtual bool shouldMarkAsDebuggee(FrameIter& iter) const = 0;
+  };
+
+  // This enum is converted to and compare with bool values; NotObserving
+  // must be 0 and Observing must be 1.
+  enum IsObserving { NotObserving = 0, Observing = 1 };
+
+  /*** Methods for calling installed debugger handlers. ***********************/
+
+  // Called when a new script becomes accessible to debuggers.
+  static void onNewScript(JSContext* cx, HandleScript script);
+
+  // Called when a new wasm instance becomes accessible to debuggers.
+  static inline void onNewWasmInstance(
+      JSContext* cx, Handle<WasmInstanceObject*> wasmInstance);
+
+  /*
+   * Announce to the debugger that the context has entered a new JavaScript
+   * frame, |frame|. Call whatever hooks have been registered to observe new
+   * frames.
+   */
+  static inline MOZ_MUST_USE bool onEnterFrame(JSContext* cx,
+                                               AbstractFramePtr frame);
+
+  /*
+   * Like onEnterFrame, but for resuming execution of a generator or async
+   * function. `frame` is a new baseline or interpreter frame, but abstractly
+   * it can be identified with a particular generator frame that was
+   * suspended earlier.
+   *
+   * There is no separate user-visible Debugger.onResumeFrame hook; this
+   * fires .onEnterFrame (again, since we're re-entering the frame).
+   *
+   * Unfortunately, the interpreter and the baseline JIT arrange for this to
+   * be called in different ways. The interpreter calls it from JSOp::Resume,
+   * immediately after pushing the resumed frame; the JIT calls it from
+   * JSOp::AfterYield, just after the generator resumes. The difference
+   * should not be user-visible.
+   */
+  static inline MOZ_MUST_USE bool onResumeFrame(JSContext* cx,
+                                                AbstractFramePtr frame);
+
+  static inline NativeResumeMode onNativeCall(JSContext* cx,
+                                              const CallArgs& args,
+                                              CallReason reason);
+
+  /*
+   * Announce to the debugger a |debugger;| statement on has been
+   * encountered on the youngest JS frame on |cx|. Call whatever hooks have
+   * been registered to observe this.
+   *
+   * Note that this method is called for all |debugger;| statements,
+   * regardless of the frame's debuggee-ness.
+   */
+  static inline MOZ_MUST_USE bool onDebuggerStatement(JSContext* cx,
+                                                      AbstractFramePtr frame);
+
+  /*
+   * Announce to the debugger that an exception has been thrown and propagated
+   * to |frame|. Call whatever hooks have been registered to observe this.
+   */
+  static inline MOZ_MUST_USE bool onExceptionUnwind(JSContext* cx,
+                                                    AbstractFramePtr frame);
+
+  /*
+   * Announce to the debugger that the thread has exited a JavaScript frame,
+   * |frame|. If |ok| is true, the frame is returning normally; if |ok| is
+   * false, the frame is throwing an exception or terminating.
+   *
+   * Change cx's current exception and |frame|'s return value to reflect the
+   * changes in behavior the hooks request, if any. Return the new error/success
+   * value.
+   *
+   * This function may be called twice for the same outgoing frame; only the
+   * first call has any effect. (Permitting double calls simplifies some
+   * cases where an onPop handler's resumption value changes a return to a
+   * throw, or vice versa: we can redirect to a complete copy of the
+   * alternative path, containing its own call to onLeaveFrame.)
+   */
+  static inline MOZ_MUST_USE bool onLeaveFrame(JSContext* cx,
+                                               AbstractFramePtr frame,
+                                               jsbytecode* pc, bool ok);
+
+  // Call any breakpoint handlers for the current scripted location.
+  static MOZ_MUST_USE bool onTrap(JSContext* cx);
+
+  // Call any stepping handlers for the current scripted location.
+  static MOZ_MUST_USE bool onSingleStep(JSContext* cx);
+
+  // Notify any Debugger instances observing this promise's global that a new
+  // promise was allocated.
+  static inline void onNewPromise(JSContext* cx,
+                                  Handle<PromiseObject*> promise);
+
+  // Notify any Debugger instances observing this promise's global that the
+  // promise has settled (ie, it has either been fulfilled or rejected). Note
+  // that this is *not* equivalent to the promise resolution (ie, the promise's
+  // fate getting locked in) because you can resolve a promise with another
+  // pending promise, in which case neither promise has settled yet.
+  //
+  // This should never be called on the same promise more than once, because a
+  // promise can only make the transition from unsettled to settled once.
+  static inline void onPromiseSettled(JSContext* cx,
+                                      Handle<PromiseObject*> promise);
+
+  // Notify any Debugger instances that a new global object has been created.
+  static inline void onNewGlobalObject(JSContext* cx,
+                                       Handle<GlobalObject*> global);
+
+  /*** Methods for querying installed debugger handlers. **********************/
+
+  // Whether any debugger is observing execution in a global.
+  static bool debuggerObservesAllExecution(GlobalObject* global);
+
+  // Whether any debugger is observing JS execution coverage in a global.
+  static bool debuggerObservesCoverage(GlobalObject* global);
+
+  // Whether any Debugger is observing asm.js execution in a global.
+  static bool debuggerObservesAsmJS(GlobalObject* global);
+
+  /*
+   * Return true if the given global is being observed by at least one
+   * Debugger that is tracking allocations.
+   */
+  static bool isObservedByDebuggerTrackingAllocations(
+      const GlobalObject& debuggee);
+
+  // If any debuggers are tracking allocations for a global, return the
+  // probability that a given allocation should be tracked. Nothing otherwise.
+  static mozilla::Maybe<double> allocationSamplingProbability(
+      GlobalObject* global);
+
+  // Whether any debugger is observing exception unwinds in a realm.
+  static bool hasExceptionUnwindHook(GlobalObject* global);
+
+  // Whether any debugger is observing debugger statements in a realm.
+  static bool hasDebuggerStatementHook(GlobalObject* global);
+
+  /*** Assorted methods for interacting with the runtime. *********************/
+
+  // Checks if the current compartment is allowed to execute code.
+  static inline MOZ_MUST_USE bool checkNoExecute(JSContext* cx,
+                                                 HandleScript script);
+
+  /*
+   * Announce to the debugger that a generator object has been created,
+   * via JSOp::Generator.
+   *
+   * This does not fire user hooks, but it's needed for debugger bookkeeping.
+   */
+  static inline MOZ_MUST_USE bool onNewGenerator(
+      JSContext* cx, AbstractFramePtr frame,
+      Handle<AbstractGeneratorObject*> genObj);
+
+  // If necessary, record an object that was just allocated for any observing
+  // debuggers.
+  static inline MOZ_MUST_USE bool onLogAllocationSite(JSContext* cx,
+                                                      JSObject* obj,
+                                                      HandleSavedFrame frame,
+                                                      mozilla::TimeStamp when);
+
+  // Announce to the debugger that a global object is being collected by the
+  // specified major GC.
+  static inline void notifyParticipatesInGC(GlobalObject* global,
+                                            uint64_t majorGCNumber);
+
+  /*
+   * Get any instrumentation ID which has been associated with a script using
+   * the specified debugger object.
+   */
+  static bool getScriptInstrumentationId(JSContext* cx, HandleObject dbgObject,
+                                         HandleScript script,
+                                         MutableHandleValue rval);
+
+ private:
+  static bool stepModeEnabledSlow(JSScript* script);
+  static bool hasBreakpointsAtSlow(JSScript* script, jsbytecode* pc);
+  static void slowPathOnNewGlobalObject(JSContext* cx,
+                                        Handle<GlobalObject*> global);
+  static void slowPathNotifyParticipatesInGC(uint64_t majorGCNumber,
+                                             JS::Realm::DebuggerVector& dbgs);
+  static MOZ_MUST_USE bool slowPathOnLogAllocationSite(
+      JSContext* cx, HandleObject obj, HandleSavedFrame frame,
+      mozilla::TimeStamp when, JS::Realm::DebuggerVector& dbgs);
+  static MOZ_MUST_USE bool slowPathOnLeaveFrame(JSContext* cx,
+                                                AbstractFramePtr frame,
+                                                jsbytecode* pc, bool ok);
+  static MOZ_MUST_USE bool slowPathOnNewGenerator(
+      JSContext* cx, AbstractFramePtr frame,
+      Handle<AbstractGeneratorObject*> genObj);
+  static MOZ_MUST_USE bool slowPathCheckNoExecute(JSContext* cx,
+                                                  HandleScript script);
+  static MOZ_MUST_USE bool slowPathOnEnterFrame(JSContext* cx,
+                                                AbstractFramePtr frame);
+  static MOZ_MUST_USE bool slowPathOnResumeFrame(JSContext* cx,
+                                                 AbstractFramePtr frame);
+  static NativeResumeMode slowPathOnNativeCall(JSContext* cx,
+                                               const CallArgs& args,
+                                               CallReason reason);
+  static MOZ_MUST_USE bool slowPathOnDebuggerStatement(JSContext* cx,
+                                                       AbstractFramePtr frame);
+  static MOZ_MUST_USE bool slowPathOnExceptionUnwind(JSContext* cx,
+                                                     AbstractFramePtr frame);
+  static void slowPathOnNewWasmInstance(
+      JSContext* cx, Handle<WasmInstanceObject*> wasmInstance);
+  static void slowPathOnNewPromise(JSContext* cx,
+                                   Handle<PromiseObject*> promise);
+  static void slowPathOnPromiseSettled(JSContext* cx,
+                                       Handle<PromiseObject*> promise);
+  static bool inFrameMaps(AbstractFramePtr frame);
+  static void slowPathTraceGeneratorFrame(JSTracer* tracer,
+                                          AbstractGeneratorObject* generator);
+};
+
+// Suppresses all debuggee NX checks, i.e., allow all execution. Used to allow
+// certain whitelisted operations to execute code.
+//
+// WARNING
+// WARNING Do not use this unless you know what you are doing!
+// WARNING
+class AutoSuppressDebuggeeNoExecuteChecks {
+  EnterDebuggeeNoExecute** stack_;
+  EnterDebuggeeNoExecute* prev_;
+
+ public:
+  explicit AutoSuppressDebuggeeNoExecuteChecks(JSContext* cx) {
+    stack_ = &cx->noExecuteDebuggerTop.ref();
+    prev_ = *stack_;
+    *stack_ = nullptr;
+  }
+
+  ~AutoSuppressDebuggeeNoExecuteChecks() {
+    MOZ_ASSERT(!*stack_);
+    *stack_ = prev_;
+  }
+};
+
+} /* namespace js */
+
+#endif /* debugger_DebugAPI_h */
diff --git a/js/src/debugger/DebugScript.cpp b/js/src/debugger/DebugScript.cpp
new file mode 100644
index 0000000000..caa4f30f88
--- /dev/null
+++ b/js/src/debugger/DebugScript.cpp
@@ -0,0 +1,344 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/DebugScript.h"
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType
+#include "mozilla/HashTable.h"   // for HashMapEntry, HashTable<>::Ptr, HashMap
+#include "mozilla/UniquePtr.h"   // for UniquePtr
+
+#include <utility>  // for std::move
+
+#include "jsapi.h"
+
+#include "debugger/DebugAPI.h"    // for DebugAPI
+#include "debugger/Debugger.h"    // for JSBreakpointSite, Breakpoint
+#include "gc/Cell.h"              // for TenuredCell
+#include "gc/FreeOp.h"            // for JSFreeOp
+#include "gc/GCEnum.h"            // for MemoryUse, MemoryUse::BreakpointSite
+#include "gc/Marking.h"           // for IsAboutToBeFinalized
+#include "gc/Zone.h"              // for Zone
+#include "gc/ZoneAllocator.h"     // for AddCellMemory
+#include "jit/BaselineJIT.h"      // for BaselineScript
+#include "vm/BytecodeIterator.h"  // for AllBytecodesIterable
+#include "vm/JSContext.h"         // for JSContext
+#include "vm/JSScript.h"          // for JSScript, DebugScriptMap
+#include "vm/NativeObject.h"      // for NativeObject
+#include "vm/Realm.h"             // for Realm, AutoRealm
+#include "vm/Runtime.h"           // for ReportOutOfMemory
+#include "vm/Stack.h"             // for ActivationIterator, Activation
+
+#include "gc/FreeOp-inl.h"            // for JSFreeOp::free_
+#include "gc/GC-inl.h"                // for ZoneCellIter
+#include "gc/Marking-inl.h"           // for CheckGCThingAfterMovingGC
+#include "gc/WeakMap-inl.h"           // for WeakMap::remove
+#include "vm/BytecodeIterator-inl.h"  // for AllBytecodesIterable
+#include "vm/JSContext-inl.h"         // for JSContext::check
+#include "vm/JSScript-inl.h"          // for JSScript::hasBaselineScript
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+
+namespace js {
+
+/* static */
+DebugScript* DebugScript::get(JSScript* script) {
+  MOZ_ASSERT(script->hasDebugScript());
+  DebugScriptMap* map = script->zone()->debugScriptMap.get();
+  MOZ_ASSERT(map);
+  DebugScriptMap::Ptr p = map->lookup(script);
+  MOZ_ASSERT(p);
+  return p->value().get();
+}
+
+/* static */
+DebugScript* DebugScript::getOrCreate(JSContext* cx, JSScript* script) {
+  if (script->hasDebugScript()) {
+    return get(script);
+  }
+
+  size_t nbytes = allocSize(script->length());
+  UniqueDebugScript debug(
+      reinterpret_cast<DebugScript*>(cx->pod_calloc<uint8_t>(nbytes)));
+  if (!debug) {
+    return nullptr;
+  }
+
+  /* Create zone's debugScriptMap if necessary. */
+  if (!script->zone()->debugScriptMap) {
+    auto map = cx->make_unique<DebugScriptMap>();
+    if (!map) {
+      return nullptr;
+    }
+
+    script->zone()->debugScriptMap = std::move(map);
+  }
+
+  MOZ_ASSERT(script->hasBytecode());
+
+  DebugScript* borrowed = debug.get();
+  if (!script->zone()->debugScriptMap->putNew(script, std::move(debug))) {
+    ReportOutOfMemory(cx);
+    return nullptr;
+  }
+
+  // It is safe to set this: we can't fail after this point.
+  script->setHasDebugScript(true);
+  AddCellMemory(script, nbytes, MemoryUse::ScriptDebugScript);
+
+  /*
+   * Ensure that any Interpret() instances running on this script have
+   * interrupts enabled. The interrupts must stay enabled until the
+   * debug state is destroyed.
+   */
+  for (ActivationIterator iter(cx); !iter.done(); ++iter) {
+    if (iter->isInterpreter()) {
+      iter->asInterpreter()->enableInterruptsIfRunning(script);
+    }
+  }
+
+  return borrowed;
+}
+
+/* static */
+JSBreakpointSite* DebugScript::getBreakpointSite(JSScript* script,
+                                                 jsbytecode* pc) {
+  uint32_t offset = script->pcToOffset(pc);
+  return script->hasDebugScript() ? get(script)->breakpoints[offset] : nullptr;
+}
+
+/* static */
+JSBreakpointSite* DebugScript::getOrCreateBreakpointSite(JSContext* cx,
+                                                         JSScript* script,
+                                                         jsbytecode* pc) {
+  AutoRealm ar(cx, script);
+
+  DebugScript* debug = getOrCreate(cx, script);
+  if (!debug) {
+    return nullptr;
+  }
+
+  JSBreakpointSite*& site = debug->breakpoints[script->pcToOffset(pc)];
+
+  if (!site) {
+    site = cx->new_<JSBreakpointSite>(script, pc);
+    if (!site) {
+      return nullptr;
+    }
+    debug->numSites++;
+    AddCellMemory(script, sizeof(JSBreakpointSite), MemoryUse::BreakpointSite);
+
+    if (script->hasBaselineScript()) {
+      script->baselineScript()->toggleDebugTraps(script, pc);
+    }
+  }
+
+  return site;
+}
+
+/* static */
+void DebugScript::destroyBreakpointSite(JSFreeOp* fop, JSScript* script,
+                                        jsbytecode* pc) {
+  DebugScript* debug = get(script);
+  JSBreakpointSite*& site = debug->breakpoints[script->pcToOffset(pc)];
+  MOZ_ASSERT(site);
+  MOZ_ASSERT(site->isEmpty());
+
+  site->delete_(fop);
+  site = nullptr;
+
+  debug->numSites--;
+  if (!debug->needed()) {
+    DebugAPI::destroyDebugScript(fop, script);
+  }
+
+  if (script->hasBaselineScript()) {
+    script->baselineScript()->toggleDebugTraps(script, pc);
+  }
+}
+
+/* static */
+void DebugScript::clearBreakpointsIn(JSFreeOp* fop, JSScript* script,
+                                     Debugger* dbg, JSObject* handler) {
+  MOZ_ASSERT(script);
+  // Breakpoints hold wrappers in the script's compartment for the handler. Make
+  // sure we don't try to search for the unwrapped handler.
+  MOZ_ASSERT_IF(handler, script->compartment() == handler->compartment());
+
+  if (!script->hasDebugScript()) {
+    return;
+  }
+
+  AllBytecodesIterable iter(script);
+  for (BytecodeLocation loc : iter) {
+    JSBreakpointSite* site = getBreakpointSite(script, loc.toRawBytecode());
+    if (site) {
+      Breakpoint* nextbp;
+      for (Breakpoint* bp = site->firstBreakpoint(); bp; bp = nextbp) {
+        nextbp = bp->nextInSite();
+        if ((!dbg || bp->debugger == dbg) &&
+            (!handler || bp->getHandler() == handler)) {
+          bp->remove(fop);
+        }
+      }
+    }
+  }
+}
+
+#ifdef DEBUG
+/* static */
+uint32_t DebugScript::getStepperCount(JSScript* script) {
+  return script->hasDebugScript() ? get(script)->stepperCount : 0;
+}
+#endif  // DEBUG
+
+/* static */
+bool DebugScript::incrementStepperCount(JSContext* cx, JSScript* script) {
+  cx->check(script);
+  MOZ_ASSERT(cx->realm()->isDebuggee());
+
+  AutoRealm ar(cx, script);
+
+  DebugScript* debug = getOrCreate(cx, script);
+  if (!debug) {
+    return false;
+  }
+
+  debug->stepperCount++;
+
+  if (debug->stepperCount == 1) {
+    if (script->hasBaselineScript()) {
+      script->baselineScript()->toggleDebugTraps(script, nullptr);
+    }
+  }
+
+  return true;
+}
+
+/* static */
+void DebugScript::decrementStepperCount(JSFreeOp* fop, JSScript* script) {
+  DebugScript* debug = get(script);
+  MOZ_ASSERT(debug);
+  MOZ_ASSERT(debug->stepperCount > 0);
+
+  debug->stepperCount--;
+
+  if (debug->stepperCount == 0) {
+    if (script->hasBaselineScript()) {
+      script->baselineScript()->toggleDebugTraps(script, nullptr);
+    }
+
+    if (!debug->needed()) {
+      DebugAPI::destroyDebugScript(fop, script);
+    }
+  }
+}
+
+/* static */
+bool DebugScript::incrementGeneratorObserverCount(JSContext* cx,
+                                                  JSScript* script) {
+  cx->check(script);
+  MOZ_ASSERT(cx->realm()->isDebuggee());
+
+  AutoRealm ar(cx, script);
+
+  DebugScript* debug = getOrCreate(cx, script);
+  if (!debug) {
+    return false;
+  }
+
+  debug->generatorObserverCount++;
+
+  // It is our caller's responsibility, before bumping the generator observer
+  // count, to make sure that the baseline code includes the necessary
+  // JSOp::AfterYield instrumentation by calling
+  // {ensure,update}ExecutionObservabilityOfScript.
+  MOZ_ASSERT_IF(script->hasBaselineScript(),
+                script->baselineScript()->hasDebugInstrumentation());
+
+  return true;
+}
+
+/* static */
+void DebugScript::decrementGeneratorObserverCount(JSFreeOp* fop,
+                                                  JSScript* script) {
+  DebugScript* debug = get(script);
+  MOZ_ASSERT(debug);
+  MOZ_ASSERT(debug->generatorObserverCount > 0);
+
+  debug->generatorObserverCount--;
+
+  if (!debug->needed()) {
+    DebugAPI::destroyDebugScript(fop, script);
+  }
+}
+
+/* static */
+void DebugAPI::traceDebugScript(JSTracer* trc, JSScript* script) {
+  MOZ_ASSERT(script->hasDebugScript());
+  DebugScript::get(script)->trace(trc, script);
+}
+
+void DebugScript::trace(JSTracer* trc, JSScript* owner) {
+  size_t length = owner->length();
+  for (size_t i = 0; i < length; i++) {
+    JSBreakpointSite* site = breakpoints[i];
+    if (site) {
+      site->trace(trc);
+    }
+  }
+}
+
+/* static */
+void DebugAPI::destroyDebugScript(JSFreeOp* fop, JSScript* script) {
+  if (script->hasDebugScript()) {
+    DebugScriptMap* map = script->zone()->debugScriptMap.get();
+    MOZ_ASSERT(map);
+    DebugScriptMap::Ptr p = map->lookup(script);
+    MOZ_ASSERT(p);
+    DebugScript* debug = p->value().release();
+    map->remove(p);
+    script->setHasDebugScript(false);
+
+    debug->delete_(fop, script);
+  }
+}
+
+void DebugScript::delete_(JSFreeOp* fop, JSScript* owner) {
+  size_t length = owner->length();
+  for (size_t i = 0; i < length; i++) {
+    JSBreakpointSite* site = breakpoints[i];
+    if (site) {
+      site->delete_(fop);
+    }
+  }
+
+  fop->free_(owner, this, allocSize(owner->length()),
+             MemoryUse::ScriptDebugScript);
+}
+
+#ifdef JSGC_HASH_TABLE_CHECKS
+/* static */
+void DebugAPI::checkDebugScriptAfterMovingGC(DebugScript* ds) {
+  for (uint32_t i = 0; i < ds->numSites; i++) {
+    JSBreakpointSite* site = ds->breakpoints[i];
+    if (site) {
+      CheckGCThingAfterMovingGC(site->script.get());
+    }
+  }
+}
+#endif  // JSGC_HASH_TABLE_CHECKS
+
+/* static */
+bool DebugAPI::stepModeEnabledSlow(JSScript* script) {
+  return DebugScript::get(script)->stepperCount > 0;
+}
+
+/* static */
+bool DebugAPI::hasBreakpointsAtSlow(JSScript* script, jsbytecode* pc) {
+  JSBreakpointSite* site = DebugScript::getBreakpointSite(script, pc);
+  return !!site;
+}
+
+}  // namespace js
diff --git a/js/src/debugger/DebugScript.h b/js/src/debugger/DebugScript.h
new file mode 100644
index 0000000000..9a6e5561e8
--- /dev/null
+++ b/js/src/debugger/DebugScript.h
@@ -0,0 +1,122 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef dbg_DebugScript_h
+#define dbg_DebugScript_h
+
+#include <stddef.h>  // for offsetof
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for uint32_t
+
+#include "jsapi.h"
+#include "jstypes.h"
+
+namespace JS {
+class JS_PUBLIC_API Realm;
+}
+
+namespace js {
+
+class JSBreakpointSite;
+class Debugger;
+
+// DebugScript manages the internal debugger state for a JSScript, which may be
+// associated with multiple Debuggers.
+class DebugScript {
+  friend class DebugAPI;
+
+  /*
+   * If this is a generator script, this is the number of Debugger.Frames
+   * referring to calls to this generator, whether live or suspended. Closed
+   * generators do not contribute a count.
+   *
+   * When greater than zero, this script should be compiled with debug
+   * instrumentation to call Debugger::onResumeFrame at each resumption site, so
+   * that Debugger can reconnect any extant Debugger.Frames with the new
+   * concrete frame.
+   */
+  uint32_t generatorObserverCount;
+
+  /*
+   * The number of Debugger.Frame objects that refer to frames running this
+   * script and that have onStep handlers. When nonzero, the interpreter and JIT
+   * must arrange to call Debugger::onSingleStep before each bytecode, or at
+   * least at some useful granularity.
+   */
+  uint32_t stepperCount;
+
+  /*
+   * Number of breakpoint sites at opcodes in the script. This is the number
+   * of populated entries in DebugScript::breakpoints, below.
+   */
+  uint32_t numSites;
+
+  /*
+   * Breakpoints set in our script. For speed and simplicity, this array is
+   * parallel to script->code(): the JSBreakpointSite for the opcode at
+   * script->code()[offset] is debugScript->breakpoints[offset]. Naturally,
+   * this array's true length is script->length().
+   */
+  JSBreakpointSite* breakpoints[1];
+
+  /*
+   * True if this DebugScript carries any useful information. If false, it
+   * should be removed from its JSScript.
+   */
+  bool needed() const {
+    return generatorObserverCount > 0 || stepperCount > 0 || numSites > 0;
+  }
+
+  static size_t allocSize(size_t codeLength) {
+    return offsetof(DebugScript, breakpoints) +
+           codeLength * sizeof(JSBreakpointSite*);
+  }
+
+  void trace(JSTracer* trc, JSScript* owner);
+  void delete_(JSFreeOp* fop, JSScript* owner);
+
+  static DebugScript* get(JSScript* script);
+  static DebugScript* getOrCreate(JSContext* cx, JSScript* script);
+
+ public:
+  static JSBreakpointSite* getBreakpointSite(JSScript* script, jsbytecode* pc);
+  static JSBreakpointSite* getOrCreateBreakpointSite(JSContext* cx,
+                                                     JSScript* script,
+                                                     jsbytecode* pc);
+  static void destroyBreakpointSite(JSFreeOp* fop, JSScript* script,
+                                    jsbytecode* pc);
+
+  static void clearBreakpointsIn(JSFreeOp* fop, JSScript* script, Debugger* dbg,
+                                 JSObject* handler);
+
+#ifdef DEBUG
+  static uint32_t getStepperCount(JSScript* script);
+#endif
+
+  /*
+   * Increment or decrement the single-step count. If the count is non-zero
+   * then the script is in single-step mode.
+   *
+   * Only incrementing is fallible, as it could allocate a DebugScript.
+   */
+  static MOZ_MUST_USE bool incrementStepperCount(JSContext* cx,
+                                                 JSScript* script);
+  static void decrementStepperCount(JSFreeOp* fop, JSScript* script);
+
+  /*
+   * Increment or decrement the generator observer count. If the count is
+   * non-zero then the script reports resumptions to the debugger.
+   *
+   * Only incrementing is fallible, as it could allocate a DebugScript.
+   */
+  static MOZ_MUST_USE bool incrementGeneratorObserverCount(JSContext* cx,
+                                                           JSScript* script);
+  static void decrementGeneratorObserverCount(JSFreeOp* fop, JSScript* script);
+};
+
+} /* namespace js */
+
+#endif /* dbg_DebugScript_h */
diff --git a/js/src/debugger/Debugger-inl.h b/js/src/debugger/Debugger-inl.h
new file mode 100644
index 0000000000..5b0fafb8ad
--- /dev/null
+++ b/js/src/debugger/Debugger-inl.h
@@ -0,0 +1,31 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Debugger_inl_h
+#define debugger_Debugger_inl_h
+
+#include "debugger/Debugger.h"  // for Debugger, ResumeMode
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType
+
+#include "vm/JSObject.h"      // for JSObject
+#include "vm/NativeObject.h"  // for NativeObject, JSObject::is
+
+/* static */ inline js::Debugger* js::Debugger::fromJSObject(
+    const JSObject* obj) {
+  MOZ_ASSERT(obj->is<DebuggerInstanceObject>());
+  return (Debugger*)obj->as<NativeObject>().getPrivate();
+}
+
+inline bool js::Debugger::isHookCallAllowed(JSContext* cx) const {
+  // If we are evaluating inside of an eval on a debugger that has an
+  // onNativeCall hook, we want to _only_ call the hooks attached to that
+  // specific debugger.
+  return !cx->insideDebuggerEvaluationWithOnNativeCallHook ||
+         this == cx->insideDebuggerEvaluationWithOnNativeCallHook;
+}
+
+#endif /* debugger_Debugger_inl_h */
diff --git a/js/src/debugger/Debugger.cpp b/js/src/debugger/Debugger.cpp
new file mode 100644
index 0000000000..1736a96a71
--- /dev/null
+++ b/js/src/debugger/Debugger.cpp
@@ -0,0 +1,6954 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Debugger-inl.h"
+
+#include "mozilla/Attributes.h"        // for MOZ_STACK_CLASS, MOZ_RAII
+#include "mozilla/DebugOnly.h"         // for DebugOnly
+#include "mozilla/DoublyLinkedList.h"  // for DoublyLinkedList<>::Iterator
+#include "mozilla/HashTable.h"         // for HashSet<>::Range, HashMapEntry
+#include "mozilla/Maybe.h"             // for Maybe, Nothing, Some
+#include "mozilla/ScopeExit.h"         // for MakeScopeExit, ScopeExit
+#include "mozilla/ThreadLocal.h"       // for ThreadLocal
+#include "mozilla/TimeStamp.h"         // for TimeStamp, TimeDuration
+#include "mozilla/UniquePtr.h"         // for UniquePtr
+#include "mozilla/Variant.h"           // for AsVariant, AsVariantTemporary
+#include "mozilla/Vector.h"            // for Vector, Vector<>::ConstRange
+
+#include <algorithm>   // for std::find, std::max
+#include <functional>  // for function
+#include <stddef.h>    // for size_t
+#include <stdint.h>    // for uint32_t, uint64_t, int32_t
+#include <string.h>    // for strlen, strcmp
+#include <utility>     // for std::move
+
+#include "jsapi.h"    // for CallArgs, CallArgsFromVp
+#include "jstypes.h"  // for JS_PUBLIC_API
+
+#include "builtin/Array.h"               // for NewDenseFullyAllocatedArray
+#include "debugger/DebugAPI.h"           // for ResumeMode, DebugAPI
+#include "debugger/DebuggerMemory.h"     // for DebuggerMemory
+#include "debugger/DebugScript.h"        // for DebugScript
+#include "debugger/Environment.h"        // for DebuggerEnvironment
+#include "debugger/Frame.h"              // for DebuggerFrame
+#include "debugger/NoExecute.h"          // for EnterDebuggeeNoExecute
+#include "debugger/Object.h"             // for DebuggerObject
+#include "debugger/Script.h"             // for DebuggerScript
+#include "debugger/Source.h"             // for DebuggerSource
+#include "frontend/CompilationInfo.h"    // for CompilationStencil
+#include "frontend/NameAnalysisTypes.h"  // for ParseGoal, ParseGoal::Script
+#include "frontend/ParseContext.h"       // for UsedNameTracker
+#include "frontend/Parser.h"             // for Parser
+#include "gc/FreeOp.h"                   // for JSFreeOp
+#include "gc/GC.h"                       // for IterateScripts
+#include "gc/GCMarker.h"                 // for GCMarker
+#include "gc/GCRuntime.h"                // for GCRuntime, AutoEnterIteration
+#include "gc/HashUtil.h"                 // for DependentAddPtr
+#include "gc/Marking.h"                  // for IsMarkedUnbarriered, IsMarked
+#include "gc/PublicIterators.h"          // for RealmsIter, CompartmentsIter
+#include "gc/Rooting.h"                  // for RootedNativeObject
+#include "gc/Statistics.h"               // for Statistics::SliceData
+#include "gc/Tracer.h"                   // for TraceEdge
+#include "gc/Zone.h"                     // for Zone
+#include "gc/ZoneAllocator.h"            // for ZoneAllocPolicy
+#include "jit/BaselineDebugModeOSR.h"  // for RecompileOnStackBaselineScriptsForDebugMode
+#include "jit/BaselineJIT.h"           // for FinishDiscardBaselineScript
+#include "jit/Invalidation.h"         // for RecompileInfoVector
+#include "jit/Ion.h"                  // for JitContext
+#include "jit/JitScript.h"            // for JitScript
+#include "jit/JSJitFrameIter.h"       // for InlineFrameIterator
+#include "jit/RematerializedFrame.h"  // for RematerializedFrame
+#include "js/Conversions.h"           // for ToBoolean, ToUint32
+#include "js/Debug.h"                 // for Builder::Object, Builder
+#include "js/friend/ErrorMessages.h"  // for GetErrorMessage, JSMSG_*
+#include "js/GCAPI.h"                 // for GarbageCollectionEvent
+#include "js/HeapAPI.h"               // for ExposeObjectToActiveJS
+#include "js/Promise.h"               // for AutoDebuggerJobQueueInterruption
+#include "js/Proxy.h"                 // for PropertyDescriptor
+#include "js/SourceText.h"            // for SourceOwnership, SourceText
+#include "js/StableStringChars.h"     // for AutoStableStringChars
+#include "js/UbiNode.h"               // for Node, RootList, Edge
+#include "js/UbiNodeBreadthFirst.h"   // for BreadthFirst
+#include "js/Warnings.h"              // for AutoSuppressWarningReporter
+#include "js/Wrapper.h"               // for CheckedUnwrapStatic
+#include "util/Text.h"                // for DuplicateString, js_strlen
+#include "vm/ArrayObject.h"           // for ArrayObject
+#include "vm/AsyncFunction.h"         // for AsyncFunctionGeneratorObject
+#include "vm/AsyncIteration.h"        // for AsyncGeneratorObject
+#include "vm/BytecodeUtil.h"          // for JSDVG_IGNORE_STACK
+#include "vm/Compartment.h"           // for CrossCompartmentKey
+#include "vm/EnvironmentObject.h"     // for IsSyntacticEnvironment
+#include "vm/ErrorReporting.h"        // for ReportErrorToGlobal
+#include "vm/GeneratorObject.h"       // for AbstractGeneratorObject
+#include "vm/GlobalObject.h"          // for GlobalObject
+#include "vm/Interpreter.h"           // for Call, ReportIsNotFunction
+#include "vm/Iteration.h"             // for CreateIterResultObject
+#include "vm/JSAtom.h"                // for Atomize, ClassName
+#include "vm/JSContext.h"             // for JSContext
+#include "vm/JSFunction.h"            // for JSFunction
+#include "vm/JSObject.h"              // for JSObject, RequireObject
+#include "vm/ObjectGroup.h"           // for TenuredObject
+#include "vm/ObjectOperations.h"      // for DefineDataProperty
+#include "vm/PlainObject.h"           // for js::PlainObject
+#include "vm/PromiseObject.h"         // for js::PromiseObject
+#include "vm/ProxyObject.h"           // for ProxyObject, JSObject::is
+#include "vm/Realm.h"                 // for AutoRealm, Realm
+#include "vm/Runtime.h"               // for ReportOutOfMemory, JSRuntime
+#include "vm/SavedFrame.h"            // for SavedFrame
+#include "vm/SavedStacks.h"           // for SavedStacks
+#include "vm/Scope.h"                 // for Scope
+#include "vm/StringType.h"            // for JSString, PropertyName
+#include "vm/TraceLogging.h"          // for TraceLoggerForCurrentThread
+#include "vm/WrapperObject.h"         // for CrossCompartmentWrapperObject
+#include "wasm/WasmDebug.h"           // for DebugState
+#include "wasm/WasmInstance.h"        // for Instance
+#include "wasm/WasmJS.h"              // for WasmInstanceObject
+#include "wasm/WasmRealm.h"           // for Realm
+#include "wasm/WasmTypes.h"           // for WasmInstanceObjectVector
+
+#include "debugger/DebugAPI-inl.h"
+#include "debugger/Environment-inl.h"  // for DebuggerEnvironment::owner
+#include "debugger/Frame-inl.h"        // for DebuggerFrame::hasGeneratorInfo
+#include "debugger/Object-inl.h"   // for DebuggerObject::owner and isInstance.
+#include "debugger/Script-inl.h"   // for DebuggerScript::getReferent
+#include "gc/GC-inl.h"             // for ZoneCellIter
+#include "gc/Marking-inl.h"        // for MaybeForwarded
+#include "gc/WeakMap-inl.h"        // for DebuggerWeakMap::trace
+#include "vm/Compartment-inl.h"    // for Compartment::wrap
+#include "vm/GeckoProfiler-inl.h"  // for AutoSuppressProfilerSampling
+#include "vm/JSAtom-inl.h"         // for AtomToId, ValueToId
+#include "vm/JSContext-inl.h"      // for JSContext::check
+#include "vm/JSObject-inl.h"  // for JSObject::isCallable, NewTenuredObjectWithGivenProto
+#include "vm/JSScript-inl.h"      // for JSScript::isDebuggee, JSScript
+#include "vm/NativeObject-inl.h"  // for NativeObject::ensureDenseInitializedLength
+#include "vm/ObjectOperations-inl.h"  // for GetProperty, HasProperty
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+#include "vm/Stack-inl.h"             // for AbstractFramePtr::script
+
+namespace js {
+
+namespace frontend {
+class FullParseHandler;
+}
+
+namespace gc {
+struct Cell;
+}
+
+namespace jit {
+class BaselineFrame;
+}
+
+} /* namespace js */
+
+using namespace js;
+
+using JS::AutoStableStringChars;
+using JS::CompileOptions;
+using JS::SourceOwnership;
+using JS::SourceText;
+using JS::dbg::AutoEntryMonitor;
+using JS::dbg::Builder;
+using js::frontend::IsIdentifier;
+using mozilla::AsVariant;
+using mozilla::DebugOnly;
+using mozilla::MakeScopeExit;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+/*** Utils ******************************************************************/
+
+bool js::IsInterpretedNonSelfHostedFunction(JSFunction* fun) {
+  return fun->isInterpreted() && !fun->isSelfHostedBuiltin();
+}
+
+JSScript* js::GetOrCreateFunctionScript(JSContext* cx, HandleFunction fun) {
+  MOZ_ASSERT(IsInterpretedNonSelfHostedFunction(fun));
+  AutoRealm ar(cx, fun);
+  return JSFunction::getOrCreateScript(cx, fun);
+}
+
+ArrayObject* js::GetFunctionParameterNamesArray(JSContext* cx,
+                                                HandleFunction fun) {
+  RootedValueVector names(cx);
+
+  // The default value for each argument is |undefined|.
+  if (!names.growBy(fun->nargs())) {
+    return nullptr;
+  }
+
+  if (IsInterpretedNonSelfHostedFunction(fun) && fun->nargs() > 0) {
+    RootedScript script(cx, GetOrCreateFunctionScript(cx, fun));
+    if (!script) {
+      return nullptr;
+    }
+
+    MOZ_ASSERT(fun->nargs() == script->numArgs());
+
+    PositionalFormalParameterIter fi(script);
+    for (size_t i = 0; i < fun->nargs(); i++, fi++) {
+      MOZ_ASSERT(fi.argumentSlot() == i);
+      if (JSAtom* atom = fi.name()) {
+        cx->markAtom(atom);
+        names[i].setString(atom);
+      }
+    }
+  }
+
+  return NewDenseCopiedArray(cx, names.length(), names.begin());
+}
+
+bool js::ValueToIdentifier(JSContext* cx, HandleValue v, MutableHandleId id) {
+  if (!ToPropertyKey(cx, v, id)) {
+    return false;
+  }
+  if (!JSID_IS_ATOM(id) || !IsIdentifier(JSID_TO_ATOM(id))) {
+    RootedValue val(cx, v);
+    ReportValueError(cx, JSMSG_UNEXPECTED_TYPE, JSDVG_SEARCH_STACK, val,
+                     nullptr, "not an identifier");
+    return false;
+  }
+  return true;
+}
+
+class js::AutoRestoreRealmDebugMode {
+  Realm* realm_;
+  unsigned bits_;
+
+ public:
+  explicit AutoRestoreRealmDebugMode(Realm* realm)
+      : realm_(realm), bits_(realm->debugModeBits_) {
+    MOZ_ASSERT(realm_);
+  }
+
+  ~AutoRestoreRealmDebugMode() {
+    if (realm_) {
+      realm_->debugModeBits_ = bits_;
+    }
+  }
+
+  void release() { realm_ = nullptr; }
+};
+
+/* static */
+bool DebugAPI::slowPathCheckNoExecute(JSContext* cx, HandleScript script) {
+  MOZ_ASSERT(cx->realm()->isDebuggee());
+  MOZ_ASSERT(cx->noExecuteDebuggerTop);
+  return EnterDebuggeeNoExecute::reportIfFoundInStack(cx, script);
+}
+
+static inline void NukeDebuggerWrapper(NativeObject* wrapper) {
+  // In some OOM failure cases, we need to destroy the edge to the referent,
+  // to avoid trying to trace it during untimely collections.
+  wrapper->setPrivate(nullptr);
+}
+
+static void PropagateForcedReturn(JSContext* cx, AbstractFramePtr frame,
+                                  HandleValue rval) {
+  // The Debugger's hooks may return a value that affects the completion
+  // value of the given frame. For example, a hook may return `{ return: 42 }`
+  // to terminate the frame and return `42` as the final frame result.
+  // To accomplish this, the debugger treats these return values as if
+  // execution of the JS function has been terminated without a pending
+  // exception, but with a special flag. When the error is handled by the
+  // interpreter or JIT, the special flag and the error state will be cleared
+  // and execution will continue from the end of the frame.
+  MOZ_ASSERT(!cx->isExceptionPending());
+  cx->setPropagatingForcedReturn();
+  frame.setReturnValue(rval);
+}
+
+static MOZ_MUST_USE bool AdjustGeneratorResumptionValue(JSContext* cx,
+                                                        AbstractFramePtr frame,
+                                                        ResumeMode& resumeMode,
+                                                        MutableHandleValue vp);
+
+static MOZ_MUST_USE bool ApplyFrameResumeMode(JSContext* cx,
+                                              AbstractFramePtr frame,
+                                              ResumeMode resumeMode,
+                                              HandleValue rv,
+                                              HandleSavedFrame exnStack) {
+  RootedValue rval(cx, rv);
+
+  // The value passed in here is unwrapped had has no guarantees about what
+  // compartment it may be associated with, so we explcitly wrap it into the
+  // debuggee compartment.
+  if (!cx->compartment()->wrap(cx, &rval)) {
+    return false;
+  }
+
+  if (!AdjustGeneratorResumptionValue(cx, frame, resumeMode, &rval)) {
+    return false;
+  }
+
+  switch (resumeMode) {
+    case ResumeMode::Continue:
+      break;
+
+    case ResumeMode::Throw:
+      // If we have a stack from the original throw, use it instead of
+      // associating the throw with the current execution point.
+      if (exnStack) {
+        cx->setPendingException(rval, exnStack);
+      } else {
+        cx->setPendingExceptionAndCaptureStack(rval);
+      }
+      return false;
+
+    case ResumeMode::Terminate:
+      cx->clearPendingException();
+      return false;
+
+    case ResumeMode::Return:
+      PropagateForcedReturn(cx, frame, rval);
+      return false;
+
+    default:
+      MOZ_CRASH("bad Debugger::onEnterFrame resume mode");
+  }
+
+  return true;
+}
+static bool ApplyFrameResumeMode(JSContext* cx, AbstractFramePtr frame,
+                                 ResumeMode resumeMode, HandleValue rval) {
+  RootedSavedFrame nullStack(cx);
+  return ApplyFrameResumeMode(cx, frame, resumeMode, rval, nullStack);
+}
+
+bool js::ValueToStableChars(JSContext* cx, const char* fnname,
+                            HandleValue value,
+                            AutoStableStringChars& stableChars) {
+  if (!value.isString()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_EXPECTED_TYPE, fnname, "string",
+                              InformalValueTypeName(value));
+    return false;
+  }
+  RootedLinearString linear(cx, value.toString()->ensureLinear(cx));
+  if (!linear) {
+    return false;
+  }
+  if (!stableChars.initTwoByte(cx, linear)) {
+    return false;
+  }
+  return true;
+}
+
+bool EvalOptions::setFilename(JSContext* cx, const char* filename) {
+  JS::UniqueChars copy;
+  if (filename) {
+    copy = DuplicateString(cx, filename);
+    if (!copy) {
+      return false;
+    }
+  }
+
+  filename_ = std::move(copy);
+  return true;
+}
+
+bool js::ParseEvalOptions(JSContext* cx, HandleValue value,
+                          EvalOptions& options) {
+  if (!value.isObject()) {
+    return true;
+  }
+
+  RootedObject opts(cx, &value.toObject());
+
+  RootedValue v(cx);
+  if (!JS_GetProperty(cx, opts, "url", &v)) {
+    return false;
+  }
+  if (!v.isUndefined()) {
+    RootedString url_str(cx, ToString<CanGC>(cx, v));
+    if (!url_str) {
+      return false;
+    }
+    UniqueChars url_bytes = JS_EncodeStringToLatin1(cx, url_str);
+    if (!url_bytes) {
+      return false;
+    }
+    if (!options.setFilename(cx, url_bytes.get())) {
+      return false;
+    }
+  }
+
+  if (!JS_GetProperty(cx, opts, "lineNumber", &v)) {
+    return false;
+  }
+  if (!v.isUndefined()) {
+    uint32_t lineno;
+    if (!ToUint32(cx, v, &lineno)) {
+      return false;
+    }
+    options.setLineno(lineno);
+  }
+
+  return true;
+}
+
+/*** Breakpoints ************************************************************/
+
+bool BreakpointSite::isEmpty() const { return breakpoints.isEmpty(); }
+
+void BreakpointSite::trace(JSTracer* trc) {
+  for (auto p = breakpoints.begin(); p; p++) {
+    p->trace(trc);
+  }
+}
+
+void BreakpointSite::finalize(JSFreeOp* fop) {
+  while (!breakpoints.isEmpty()) {
+    breakpoints.begin()->delete_(fop);
+  }
+}
+
+Breakpoint* BreakpointSite::firstBreakpoint() const {
+  if (isEmpty()) {
+    return nullptr;
+  }
+  return &(*breakpoints.begin());
+}
+
+bool BreakpointSite::hasBreakpoint(Breakpoint* toFind) {
+  const BreakpointList::Iterator bp(toFind);
+  for (auto p = breakpoints.begin(); p; p++) {
+    if (p == bp) {
+      return true;
+    }
+  }
+  return false;
+}
+
+Breakpoint::Breakpoint(Debugger* debugger, HandleObject wrappedDebugger,
+                       BreakpointSite* site, HandleObject handler)
+    : debugger(debugger),
+      wrappedDebugger(wrappedDebugger),
+      site(site),
+      handler(handler) {
+  MOZ_ASSERT(UncheckedUnwrap(wrappedDebugger) == debugger->object);
+  MOZ_ASSERT(handler->compartment() == wrappedDebugger->compartment());
+
+  debugger->breakpoints.pushBack(this);
+  site->breakpoints.pushBack(this);
+}
+
+void Breakpoint::trace(JSTracer* trc) {
+  TraceEdge(trc, &wrappedDebugger, "breakpoint owner");
+  TraceEdge(trc, &handler, "breakpoint handler");
+}
+
+void Breakpoint::delete_(JSFreeOp* fop) {
+  debugger->breakpoints.remove(this);
+  site->breakpoints.remove(this);
+  gc::Cell* cell = site->owningCell();
+  fop->delete_(cell, this, MemoryUse::Breakpoint);
+}
+
+void Breakpoint::remove(JSFreeOp* fop) {
+  BreakpointSite* savedSite = site;
+  delete_(fop);
+
+  savedSite->destroyIfEmpty(fop);
+}
+
+Breakpoint* Breakpoint::nextInDebugger() { return debuggerLink.mNext; }
+
+Breakpoint* Breakpoint::nextInSite() { return siteLink.mNext; }
+
+JSBreakpointSite::JSBreakpointSite(JSScript* script, jsbytecode* pc)
+    : script(script), pc(pc) {
+  MOZ_ASSERT(!DebugAPI::hasBreakpointsAt(script, pc));
+}
+
+void JSBreakpointSite::remove(JSFreeOp* fop) {
+  DebugScript::destroyBreakpointSite(fop, script, pc);
+}
+
+void JSBreakpointSite::trace(JSTracer* trc) {
+  BreakpointSite::trace(trc);
+  TraceEdge(trc, &script, "breakpoint script");
+}
+
+void JSBreakpointSite::delete_(JSFreeOp* fop) {
+  BreakpointSite::finalize(fop);
+
+  fop->delete_(script, this, MemoryUse::BreakpointSite);
+}
+
+gc::Cell* JSBreakpointSite::owningCell() { return script; }
+
+Realm* JSBreakpointSite::realm() const { return script->realm(); }
+
+WasmBreakpointSite::WasmBreakpointSite(WasmInstanceObject* instanceObject_,
+                                       uint32_t offset_)
+    : instanceObject(instanceObject_), offset(offset_) {
+  MOZ_ASSERT(instanceObject_);
+  MOZ_ASSERT(instanceObject_->instance().debugEnabled());
+}
+
+void WasmBreakpointSite::trace(JSTracer* trc) {
+  BreakpointSite::trace(trc);
+  TraceEdge(trc, &instanceObject, "breakpoint Wasm instance");
+}
+
+void WasmBreakpointSite::remove(JSFreeOp* fop) {
+  instanceObject->instance().destroyBreakpointSite(fop, offset);
+}
+
+void WasmBreakpointSite::delete_(JSFreeOp* fop) {
+  BreakpointSite::finalize(fop);
+
+  fop->delete_(instanceObject, this, MemoryUse::BreakpointSite);
+}
+
+gc::Cell* WasmBreakpointSite::owningCell() { return instanceObject; }
+
+Realm* WasmBreakpointSite::realm() const { return instanceObject->realm(); }
+
+/*** Debugger hook dispatch *************************************************/
+
+Debugger::Debugger(JSContext* cx, NativeObject* dbg)
+    : object(dbg),
+      debuggees(cx->zone()),
+      uncaughtExceptionHook(nullptr),
+      allowUnobservedAsmJS(false),
+      collectCoverageInfo(false),
+      observedGCs(cx->zone()),
+      allocationsLog(cx),
+      trackingAllocationSites(false),
+      allocationSamplingProbability(1.0),
+      maxAllocationsLogLength(DEFAULT_MAX_LOG_LENGTH),
+      allocationsLogOverflowed(false),
+      frames(cx->zone()),
+      generatorFrames(cx),
+      scripts(cx),
+      sources(cx),
+      objects(cx),
+      environments(cx),
+      wasmInstanceScripts(cx),
+      wasmInstanceSources(cx),
+#ifdef NIGHTLY_BUILD
+      traceLoggerLastDrainedSize(0),
+      traceLoggerLastDrainedIteration(0),
+#endif
+      traceLoggerScriptedCallsLastDrainedSize(0),
+      traceLoggerScriptedCallsLastDrainedIteration(0) {
+  cx->check(dbg);
+
+#ifdef JS_TRACE_LOGGING
+  TraceLoggerThread* logger = TraceLoggerForCurrentThread(cx);
+  if (logger) {
+#  ifdef NIGHTLY_BUILD
+    logger->getIterationAndSize(&traceLoggerLastDrainedIteration,
+                                &traceLoggerLastDrainedSize);
+#  endif
+    logger->getIterationAndSize(&traceLoggerScriptedCallsLastDrainedIteration,
+                                &traceLoggerScriptedCallsLastDrainedSize);
+  }
+#endif
+
+  cx->runtime()->debuggerList().insertBack(this);
+}
+
+template <typename ElementAccess>
+static void RemoveDebuggerEntry(
+    mozilla::DoublyLinkedList<Debugger, ElementAccess>& list, Debugger* dbg) {
+  // The "probably" here is because there could technically be multiple lists
+  // with this type signature and theoretically the debugger could be an entry
+  // in a different one. That is not actually possible however because there
+  // is only one list the debugger could be in.
+  if (list.ElementProbablyInList(dbg)) {
+    list.remove(dbg);
+  }
+}
+
+Debugger::~Debugger() {
+  MOZ_ASSERT(debuggees.empty());
+  allocationsLog.clear();
+
+  // Breakpoints should hold us alive, so any breakpoints remaining must be set
+  // in dying JSScripts. We should clean them up, but this never asserts. I'm
+  // not sure why.
+  MOZ_ASSERT(breakpoints.isEmpty());
+
+  // We don't have to worry about locking here since Debugger is not
+  // background finalized.
+  JSContext* cx = TlsContext.get();
+  RemoveDebuggerEntry(cx->runtime()->onNewGlobalObjectWatchers(), this);
+  RemoveDebuggerEntry(cx->runtime()->onGarbageCollectionWatchers(), this);
+}
+
+#ifdef DEBUG
+/* static */
+bool Debugger::isChildJSObject(JSObject* obj) {
+  return obj->getClass() == &DebuggerFrame::class_ ||
+         obj->getClass() == &DebuggerScript::class_ ||
+         obj->getClass() == &DebuggerSource::class_ ||
+         obj->getClass() == &DebuggerObject::class_ ||
+         obj->getClass() == &DebuggerEnvironment::class_;
+}
+#endif
+
+bool Debugger::hasMemory() const {
+  return object->getReservedSlot(JSSLOT_DEBUG_MEMORY_INSTANCE).isObject();
+}
+
+DebuggerMemory& Debugger::memory() const {
+  MOZ_ASSERT(hasMemory());
+  return object->getReservedSlot(JSSLOT_DEBUG_MEMORY_INSTANCE)
+      .toObject()
+      .as<DebuggerMemory>();
+}
+
+/*** Debugger accessors *******************************************************/
+
+bool Debugger::getFrame(JSContext* cx, const FrameIter& iter,
+                        MutableHandleValue vp) {
+  RootedDebuggerFrame result(cx);
+  if (!Debugger::getFrame(cx, iter, &result)) {
+    return false;
+  }
+  vp.setObject(*result);
+  return true;
+}
+
+bool Debugger::getFrame(JSContext* cx, MutableHandleDebuggerFrame result) {
+  RootedObject proto(
+      cx, &object->getReservedSlot(JSSLOT_DEBUG_FRAME_PROTO).toObject());
+  RootedNativeObject debugger(cx, object);
+
+  // Since there is no frame/generator data to associate with this frame, this
+  // will create a new, "terminated" Debugger.Frame object.
+  RootedDebuggerFrame frame(
+      cx, DebuggerFrame::create(cx, proto, debugger, nullptr, nullptr));
+  if (!frame) {
+    return false;
+  }
+
+  result.set(frame);
+  return true;
+}
+
+bool Debugger::getFrame(JSContext* cx, const FrameIter& iter,
+                        MutableHandleDebuggerFrame result) {
+  AbstractFramePtr referent = iter.abstractFramePtr();
+  MOZ_ASSERT_IF(referent.hasScript(), !referent.script()->selfHosted());
+
+  if (referent.hasScript() &&
+      !referent.script()->ensureHasAnalyzedArgsUsage(cx)) {
+    return false;
+  }
+
+  FrameMap::AddPtr p = frames.lookupForAdd(referent);
+  if (!p) {
+    Rooted<AbstractGeneratorObject*> genObj(cx);
+    if (referent.isGeneratorFrame()) {
+      if (referent.isFunctionFrame()) {
+        AutoRealm ar(cx, referent.callee());
+        genObj = GetGeneratorObjectForFrame(cx, referent);
+      } else {
+        MOZ_ASSERT(referent.isModuleFrame());
+        AutoRealm ar(cx, referent.script()->module());
+        genObj = GetGeneratorObjectForFrame(cx, referent);
+      }
+
+      // If this frame has a generator associated with it, but no on-stack
+      // Debugger.Frame object was found, there should not be a suspended
+      // Debugger.Frame either because otherwise slowPathOnResumeFrame would
+      // have already populated the "frames" map with a Debugger.Frame.
+      MOZ_ASSERT_IF(genObj, !generatorFrames.has(genObj));
+
+      // If the frame's generator is closed, there is no way to associate the
+      // generator with the frame successfully because there is no way to
+      // get the generator's callee script, and even if we could, having it
+      // there would in no way affect the behavior of the frame.
+      if (genObj && genObj->isClosed()) {
+        genObj = nullptr;
+      }
+
+      // If no AbstractGeneratorObject exists yet, we create a Debugger.Frame
+      // below anyway, and Debugger::onNewGenerator() will associate it
+      // with the AbstractGeneratorObject later when we hit JSOp::Generator.
+    }
+
+    // Create and populate the Debugger.Frame object.
+    RootedObject proto(
+        cx, &object->getReservedSlot(JSSLOT_DEBUG_FRAME_PROTO).toObject());
+    RootedNativeObject debugger(cx, object);
+
+    RootedDebuggerFrame frame(
+        cx, DebuggerFrame::create(cx, proto, debugger, &iter, genObj));
+    if (!frame) {
+      return false;
+    }
+
+    auto terminateDebuggerFrameGuard = MakeScopeExit([&] {
+      terminateDebuggerFrame(cx->defaultFreeOp(), this, frame, referent);
+    });
+
+    if (genObj) {
+      DependentAddPtr<GeneratorWeakMap> genPtr(cx, generatorFrames, genObj);
+      if (!genPtr.add(cx, generatorFrames, genObj, frame)) {
+        return false;
+      }
+    }
+
+    if (!ensureExecutionObservabilityOfFrame(cx, referent)) {
+      return false;
+    }
+
+    if (!frames.add(p, referent, frame)) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+
+    terminateDebuggerFrameGuard.release();
+  }
+
+  result.set(p->value());
+  return true;
+}
+
+bool Debugger::getFrame(JSContext* cx, Handle<AbstractGeneratorObject*> genObj,
+                        MutableHandleDebuggerFrame result) {
+  // To create a Debugger.Frame for a running generator, we'd also need a
+  // FrameIter for its stack frame. We could make this work by searching the
+  // stack for the generator's frame, but for the moment, we only need this
+  // function to handle generators we've found on promises' reaction records,
+  // which should always be suspended.
+  MOZ_ASSERT(genObj->isSuspended());
+
+  // Do we have an existing Debugger.Frame for this generator?
+  DependentAddPtr<GeneratorWeakMap> p(cx, generatorFrames, genObj);
+  if (p) {
+    MOZ_ASSERT(&p->value()->unwrappedGenerator() == genObj);
+    result.set(p->value());
+    return true;
+  }
+
+  // Create a new Debugger.Frame.
+  RootedObject proto(
+      cx, &object->getReservedSlot(JSSLOT_DEBUG_FRAME_PROTO).toObject());
+  RootedNativeObject debugger(cx, object);
+
+  result.set(DebuggerFrame::create(cx, proto, debugger, nullptr, genObj));
+  if (!result) {
+    return false;
+  }
+
+  if (!p.add(cx, generatorFrames, genObj, result)) {
+    terminateDebuggerFrame(cx->runtime()->defaultFreeOp(), this, result,
+                           NullFramePtr());
+    return false;
+  }
+
+  return true;
+}
+
+static bool DebuggerExists(
+    GlobalObject* global, const std::function<bool(Debugger* dbg)>& predicate) {
+  // The GC analysis can't determine that the predicate can't GC, so let it know
+  // explicitly.
+  JS::AutoSuppressGCAnalysis nogc;
+
+  for (Realm::DebuggerVectorEntry& entry : global->getDebuggers()) {
+    // Callbacks should not create new references to the debugger, so don't
+    // use a barrier. This allows this method to be called during GC.
+    if (predicate(entry.dbg.unbarrieredGet())) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */
+bool Debugger::hasLiveHook(GlobalObject* global, Hook which) {
+  return DebuggerExists(global,
+                        [=](Debugger* dbg) { return dbg->getHook(which); });
+}
+
+/* static */
+bool DebugAPI::debuggerObservesAllExecution(GlobalObject* global) {
+  return DebuggerExists(
+      global, [=](Debugger* dbg) { return dbg->observesAllExecution(); });
+}
+
+/* static */
+bool DebugAPI::debuggerObservesCoverage(GlobalObject* global) {
+  return DebuggerExists(global,
+                        [=](Debugger* dbg) { return dbg->observesCoverage(); });
+}
+
+/* static */
+bool DebugAPI::debuggerObservesAsmJS(GlobalObject* global) {
+  return DebuggerExists(global,
+                        [=](Debugger* dbg) { return dbg->observesAsmJS(); });
+}
+
+/* static */
+bool DebugAPI::hasExceptionUnwindHook(GlobalObject* global) {
+  return Debugger::hasLiveHook(global, Debugger::OnExceptionUnwind);
+}
+
+/* static */
+bool DebugAPI::hasDebuggerStatementHook(GlobalObject* global) {
+  return Debugger::hasLiveHook(global, Debugger::OnDebuggerStatement);
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */>
+bool DebuggerList<HookIsEnabledFun>::init(JSContext* cx) {
+  // Determine which debuggers will receive this event, and in what order.
+  // Make a copy of the list, since the original is mutable and we will be
+  // calling into arbitrary JS.
+  Handle<GlobalObject*> global = cx->global();
+  for (Realm::DebuggerVectorEntry& entry : global->getDebuggers()) {
+    Debugger* dbg = entry.dbg;
+    if (dbg->isHookCallAllowed(cx) && hookIsEnabled(dbg)) {
+      if (!debuggers.append(ObjectValue(*dbg->toJSObject()))) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */>
+template <typename FireHookFun /* bool (Debugger*) */>
+bool DebuggerList<HookIsEnabledFun>::dispatchHook(JSContext* cx,
+                                                  FireHookFun fireHook) {
+  // Preserve the debuggee's microtask event queue while we run the hooks, so
+  // the debugger's microtask checkpoints don't run from the debuggee's
+  // microtasks, and vice versa.
+  JS::AutoDebuggerJobQueueInterruption adjqi;
+  if (!adjqi.init(cx)) {
+    return false;
+  }
+
+  // Deliver the event to each debugger, checking again to make sure it
+  // should still be delivered.
+  Handle<GlobalObject*> global = cx->global();
+  for (Value* p = debuggers.begin(); p != debuggers.end(); p++) {
+    Debugger* dbg = Debugger::fromJSObject(&p->toObject());
+    EnterDebuggeeNoExecute nx(cx, *dbg, adjqi);
+    if (dbg->debuggees.has(global) && hookIsEnabled(dbg)) {
+      bool result =
+          dbg->enterDebuggerHook(cx, [&]() -> bool { return fireHook(dbg); });
+      adjqi.runJobs();
+      if (!result) {
+        return false;
+      }
+    }
+  }
+  return true;
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */>
+template <typename FireHookFun /* bool (Debugger*) */>
+void DebuggerList<HookIsEnabledFun>::dispatchQuietHook(JSContext* cx,
+                                                       FireHookFun fireHook) {
+  bool result =
+      dispatchHook(cx, [&](Debugger* dbg) -> bool { return fireHook(dbg); });
+
+  // dispatchHook may fail due to OOM. This OOM is not handlable at the
+  // callsites of dispatchQuietHook in the engine.
+  if (!result) {
+    cx->clearPendingException();
+  }
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */>
+template <typename FireHookFun /* bool (Debugger*, ResumeMode&, MutableHandleValue vp) */>
+bool DebuggerList<HookIsEnabledFun>::dispatchResumptionHook(
+    JSContext* cx, AbstractFramePtr frame, FireHookFun fireHook) {
+  ResumeMode resumeMode = ResumeMode::Continue;
+  RootedValue rval(cx);
+  return dispatchHook(cx,
+                      [&](Debugger* dbg) -> bool {
+                        return fireHook(dbg, resumeMode, &rval);
+                      }) &&
+         ApplyFrameResumeMode(cx, frame, resumeMode, rval);
+}
+
+JSObject* Debugger::getHook(Hook hook) const {
+  MOZ_ASSERT(hook >= 0 && hook < HookCount);
+  const Value& v = object->getReservedSlot(JSSLOT_DEBUG_HOOK_START + hook);
+  return v.isUndefined() ? nullptr : &v.toObject();
+}
+
+bool Debugger::hasAnyLiveHooks() const {
+  // A onNewGlobalObject hook does not hold its Debugger live, so its behavior
+  // is nondeterministic. This behavior is not satisfying, but it is at least
+  // documented.
+  if (getHook(OnDebuggerStatement) || getHook(OnExceptionUnwind) ||
+      getHook(OnNewScript) || getHook(OnEnterFrame)) {
+    return true;
+  }
+
+  return false;
+}
+
+/* static */
+bool DebugAPI::slowPathOnEnterFrame(JSContext* cx, AbstractFramePtr frame) {
+  return Debugger::dispatchResumptionHook(
+      cx, frame,
+      [frame](Debugger* dbg) -> bool {
+        return dbg->observesFrame(frame) && dbg->observesEnterFrame();
+      },
+      [&](Debugger* dbg, ResumeMode& resumeMode, MutableHandleValue vp)
+          -> bool { return dbg->fireEnterFrame(cx, resumeMode, vp); });
+}
+
+/* static */
+bool DebugAPI::slowPathOnResumeFrame(JSContext* cx, AbstractFramePtr frame) {
+  // Don't count on this method to be called every time a generator is
+  // resumed! This is called only if the frame's debuggee bit is set,
+  // i.e. the script has breakpoints or the frame is stepping.
+  MOZ_ASSERT(frame.isGeneratorFrame());
+  MOZ_ASSERT(frame.isDebuggee());
+
+  Rooted<AbstractGeneratorObject*> genObj(
+      cx, GetGeneratorObjectForFrame(cx, frame));
+  MOZ_ASSERT(genObj);
+
+  // If there is an OOM, we mark all of the Debugger.Frame objects terminated
+  // because we want to ensure that none of the frames are in a partially
+  // initialized state where they are in "generatorFrames" but not "frames".
+  auto terminateDebuggerFramesGuard = MakeScopeExit([&] {
+    Debugger::terminateDebuggerFrames(cx, frame);
+
+    MOZ_ASSERT(!DebugAPI::inFrameMaps(frame));
+  });
+
+  // For each debugger, if there is an existing Debugger.Frame object for the
+  // resumed `frame`, update it with the new frame pointer and make sure the
+  // frame is observable.
+  FrameIter iter(cx);
+  MOZ_ASSERT(iter.abstractFramePtr() == frame);
+  for (Realm::DebuggerVectorEntry& entry : frame.global()->getDebuggers()) {
+    Debugger* dbg = entry.dbg;
+    if (Debugger::GeneratorWeakMap::Ptr generatorEntry =
+            dbg->generatorFrames.lookup(genObj)) {
+      DebuggerFrame* frameObj = generatorEntry->value();
+      MOZ_ASSERT(&frameObj->unwrappedGenerator() == genObj);
+      if (!dbg->frames.putNew(frame, frameObj)) {
+        ReportOutOfMemory(cx);
+        return false;
+      }
+      if (!frameObj->resume(iter)) {
+        return false;
+      }
+    }
+  }
+
+  terminateDebuggerFramesGuard.release();
+
+  return slowPathOnEnterFrame(cx, frame);
+}
+
+/* static */
+NativeResumeMode DebugAPI::slowPathOnNativeCall(JSContext* cx,
+                                                const CallArgs& args,
+                                                CallReason reason) {
+  // "onNativeCall" only works consistently in the context of an explicit eval
+  // that has set the "insideDebuggerEvaluationWithOnNativeCallHook" state
+  // on the JSContext, so we fast-path this hook to bail right away if that is
+  // not currently set. If this flag is set to a _different_ debugger, the
+  // standard "isHookCallAllowed" debugger logic will apply and only hooks on
+  // that debugger will be callable.
+  if (!cx->insideDebuggerEvaluationWithOnNativeCallHook) {
+    return NativeResumeMode::Continue;
+  }
+
+  DebuggerList debuggerList(cx, [](Debugger* dbg) -> bool {
+    return dbg->getHook(Debugger::OnNativeCall);
+  });
+
+  if (!debuggerList.init(cx)) {
+    return NativeResumeMode::Abort;
+  }
+
+  if (debuggerList.empty()) {
+    return NativeResumeMode::Continue;
+  }
+
+  // The onNativeCall hook is fired when self hosted functions are called,
+  // and any other self hosted function or C++ native that is directly called
+  // by the self hosted function is considered to be part of the same
+  // native call.
+  //
+  // We check this only after checking that debuggerList has items in order
+  // to avoid unnecessary calls to cx->currentScript(), which can be expensive
+  // when the top frame is in jitcode.
+  JSScript* script = cx->currentScript();
+  if (script && script->selfHosted()) {
+    return NativeResumeMode::Continue;
+  }
+
+  RootedValue rval(cx);
+  ResumeMode resumeMode = ResumeMode::Continue;
+  bool result = debuggerList.dispatchHook(cx, [&](Debugger* dbg) -> bool {
+    return dbg->fireNativeCall(cx, args, reason, resumeMode, &rval);
+  });
+  if (!result) {
+    return NativeResumeMode::Abort;
+  }
+
+  // The value is not in any particular compartment, so it needs to be
+  // explicitly wrapped into the debuggee compartment.
+  if (!cx->compartment()->wrap(cx, &rval)) {
+    return NativeResumeMode::Abort;
+  }
+
+  switch (resumeMode) {
+    case ResumeMode::Continue:
+      break;
+
+    case ResumeMode::Throw:
+      cx->setPendingExceptionAndCaptureStack(rval);
+      return NativeResumeMode::Abort;
+
+    case ResumeMode::Terminate:
+      cx->clearPendingException();
+      return NativeResumeMode::Abort;
+
+    case ResumeMode::Return:
+      args.rval().set(rval);
+      return NativeResumeMode::Override;
+  }
+
+  return NativeResumeMode::Continue;
+}
+
+/*
+ * RAII class to mark a generator as "running" temporarily while running
+ * debugger code.
+ *
+ * When Debugger::slowPathOnLeaveFrame is called for a frame that is yielding
+ * or awaiting, its generator is in the "suspended" state. Letting script
+ * observe this state, with the generator on stack yet also reenterable, would
+ * be bad, so we mark it running while we fire events.
+ */
+class MOZ_RAII AutoSetGeneratorRunning {
+  int32_t resumeIndex_;
+  AsyncGeneratorObject::State asyncGenState_;
+  Rooted<AbstractGeneratorObject*> genObj_;
+
+ public:
+  AutoSetGeneratorRunning(JSContext* cx,
+                          Handle<AbstractGeneratorObject*> genObj)
+      : resumeIndex_(0),
+        asyncGenState_(static_cast<AsyncGeneratorObject::State>(0)),
+        genObj_(cx, genObj) {
+    if (genObj) {
+      if (!genObj->isClosed() && !genObj->isBeforeInitialYield() &&
+          genObj->isSuspended()) {
+        // Yielding or awaiting.
+        resumeIndex_ = genObj->resumeIndex();
+        genObj->setRunning();
+
+        // Async generators have additionally bookkeeping which must be
+        // adjusted when switching over to the running state.
+        if (genObj->is<AsyncGeneratorObject>()) {
+          auto* asyncGenObj = &genObj->as<AsyncGeneratorObject>();
+          asyncGenState_ = asyncGenObj->state();
+          asyncGenObj->setExecuting();
+        }
+      } else {
+        // Returning or throwing. The generator is already closed, if
+        // it was ever exposed at all.
+        genObj_ = nullptr;
+      }
+    }
+  }
+
+  ~AutoSetGeneratorRunning() {
+    if (genObj_) {
+      MOZ_ASSERT(genObj_->isRunning());
+      genObj_->setResumeIndex(resumeIndex_);
+      if (genObj_->is<AsyncGeneratorObject>()) {
+        genObj_->as<AsyncGeneratorObject>().setState(asyncGenState_);
+      }
+    }
+  }
+};
+
+/*
+ * Handle leaving a frame with debuggers watching. |frameOk| indicates whether
+ * the frame is exiting normally or abruptly. Set |cx|'s exception and/or
+ * |cx->fp()|'s return value, and return a new success value.
+ */
+/* static */
+bool DebugAPI::slowPathOnLeaveFrame(JSContext* cx, AbstractFramePtr frame,
+                                    jsbytecode* pc, bool frameOk) {
+  MOZ_ASSERT_IF(!frame.isWasmDebugFrame(), pc);
+
+  mozilla::DebugOnly<Handle<GlobalObject*>> debuggeeGlobal = cx->global();
+
+  // These are updated below, but consulted by the cleanup code we register now,
+  // so declare them here, initialized to quiescent values.
+  Rooted<Completion> completion(cx);
+  bool success = false;
+
+  auto frameMapsGuard = MakeScopeExit([&] {
+    // Clean up all Debugger.Frame instances on exit. On suspending, pass the
+    // flag that says to leave those frames `.live`. Note that if the completion
+    // is a suspension but success is false, the generator gets closed, not
+    // suspended.
+    if (success && completion.get().suspending()) {
+      Debugger::suspendGeneratorDebuggerFrames(cx, frame);
+    } else {
+      Debugger::terminateDebuggerFrames(cx, frame);
+    }
+  });
+
+  // The onPop handler and associated clean up logic should not run multiple
+  // times on the same frame. If slowPathOnLeaveFrame has already been
+  // called, the frame will not be present in the Debugger frame maps.
+  Rooted<Debugger::DebuggerFrameVector> frames(
+      cx, Debugger::DebuggerFrameVector(cx));
+  if (!Debugger::getDebuggerFrames(frame, &frames)) {
+    return false;
+  }
+  if (frames.empty()) {
+    return frameOk;
+  }
+
+  completion = Completion::fromJSFramePop(cx, frame, pc, frameOk);
+
+  ResumeMode resumeMode = ResumeMode::Continue;
+  RootedValue rval(cx);
+
+  {
+    // Preserve the debuggee's microtask event queue while we run the hooks, so
+    // the debugger's microtask checkpoints don't run from the debuggee's
+    // microtasks, and vice versa.
+    JS::AutoDebuggerJobQueueInterruption adjqi;
+    if (!adjqi.init(cx)) {
+      return false;
+    }
+
+    // This path can be hit via unwinding the stack due to over-recursion or
+    // OOM. In those cases, don't fire the frames' onPop handlers, because
+    // invoking JS will only trigger the same condition. See
+    // slowPathOnExceptionUnwind.
+    if (!cx->isThrowingOverRecursed() && !cx->isThrowingOutOfMemory()) {
+      Rooted<AbstractGeneratorObject*> genObj(
+          cx, frame.isGeneratorFrame() ? GetGeneratorObjectForFrame(cx, frame)
+                                       : nullptr);
+
+      // For each Debugger.Frame, fire its onPop handler, if any.
+      for (size_t i = 0; i < frames.length(); i++) {
+        HandleDebuggerFrame frameobj = frames[i];
+        Debugger* dbg = frameobj->owner();
+        EnterDebuggeeNoExecute nx(cx, *dbg, adjqi);
+
+        // Removing a global from a Debugger's debuggee set kills all of that
+        // Debugger's D.Fs in that global. This means that one D.F's onPop can
+        // kill the next D.F. So we have to check whether frameobj is still "on
+        // the stack".
+        if (frameobj->isOnStack() && frameobj->onPopHandler()) {
+          OnPopHandler* handler = frameobj->onPopHandler();
+
+          bool result = dbg->enterDebuggerHook(cx, [&]() -> bool {
+            ResumeMode nextResumeMode = ResumeMode::Continue;
+            RootedValue nextValue(cx);
+
+            // Call the onPop handler.
+            bool success;
+            {
+              // Mark the generator as running, to prevent reentrance.
+              //
+              // At certain points in a generator's lifetime,
+              // GetGeneratorObjectForFrame can return null even when the
+              // generator exists, but at those points the generator has not yet
+              // been exposed to JavaScript, so reentrance isn't possible
+              // anyway. So there's no harm done if this has no effect in that
+              // case.
+              AutoSetGeneratorRunning asgr(cx, genObj);
+              success = handler->onPop(cx, frameobj, completion, nextResumeMode,
+                                       &nextValue);
+            }
+
+            return dbg->processParsedHandlerResult(cx, frame, pc, success,
+                                                   nextResumeMode, nextValue,
+                                                   resumeMode, &rval);
+          });
+          adjqi.runJobs();
+
+          if (!result) {
+            return false;
+          }
+
+          // At this point, we are back in the debuggee compartment, and
+          // any error has been wrapped up as a completion value.
+          MOZ_ASSERT(!cx->isExceptionPending());
+        }
+      }
+    }
+  }
+
+  completion.get().updateFromHookResult(resumeMode, rval);
+
+  // Now that we've run all the handlers, extract the final resumption mode. */
+  ResumeMode completionResumeMode;
+  RootedValue completionValue(cx);
+  RootedSavedFrame completionStack(cx);
+  completion.get().toResumeMode(completionResumeMode, &completionValue,
+                                &completionStack);
+
+  // If we are returning the original value used to create the completion, then
+  // we don't want to treat the resumption value as a Return completion, because
+  // that would cause us to apply AdjustGeneratorResumptionValue to the
+  // already-adjusted value that the generator actually returned.
+  if (resumeMode == ResumeMode::Continue &&
+      completionResumeMode == ResumeMode::Return) {
+    completionResumeMode = ResumeMode::Continue;
+  }
+
+  if (!ApplyFrameResumeMode(cx, frame, completionResumeMode, completionValue,
+                            completionStack)) {
+    if (!cx->isPropagatingForcedReturn()) {
+      // If this is an exception or termination, we just propagate that along.
+      return false;
+    }
+
+    // Since we are leaving the frame here, we can convert a forced return
+    // into a normal return right away.
+    cx->clearPropagatingForcedReturn();
+  }
+  success = true;
+  return true;
+}
+
+/* static */
+bool DebugAPI::slowPathOnNewGenerator(JSContext* cx, AbstractFramePtr frame,
+                                      Handle<AbstractGeneratorObject*> genObj) {
+  // This is called from JSOp::Generator, after default parameter expressions
+  // are evaluated and well after onEnterFrame, so Debugger.Frame objects for
+  // `frame` may already have been exposed to debugger code. The
+  // AbstractGeneratorObject for this generator call, though, has just been
+  // created. It must be associated with any existing Debugger.Frames.
+
+  // Initializing frames with their associated generator is critical to the
+  // functionality of the debugger, so if there is an OOM, we want to
+  // cleanly terminate all of the frames.
+  auto terminateDebuggerFramesGuard =
+      MakeScopeExit([&] { Debugger::terminateDebuggerFrames(cx, frame); });
+
+  bool ok = true;
+  Debugger::forEachOnStackDebuggerFrame(
+      frame, [&](Debugger* dbg, DebuggerFrame* frameObjPtr) {
+        if (!ok) {
+          return;
+        }
+
+        RootedDebuggerFrame frameObj(cx, frameObjPtr);
+
+        AutoRealm ar(cx, frameObj);
+
+        if (!frameObj->setGeneratorInfo(cx, genObj)) {
+          // This leaves `genObj` and `frameObj` unassociated. It's OK
+          // because we won't pause again with this generator on the stack:
+          // the caller will immediately discard `genObj` and unwind `frame`.
+          ok = false;
+          return;
+        }
+
+        DependentAddPtr<Debugger::GeneratorWeakMap> genPtr(
+            cx, dbg->generatorFrames, genObj);
+        if (!genPtr.add(cx, dbg->generatorFrames, genObj, frameObj)) {
+          ok = false;
+        }
+      });
+
+  if (!ok) {
+    return false;
+  }
+
+  terminateDebuggerFramesGuard.release();
+  return true;
+}
+
+/* static */
+bool DebugAPI::slowPathOnDebuggerStatement(JSContext* cx,
+                                           AbstractFramePtr frame) {
+  return Debugger::dispatchResumptionHook(
+      cx, frame,
+      [](Debugger* dbg) -> bool {
+        return dbg->getHook(Debugger::OnDebuggerStatement);
+      },
+      [&](Debugger* dbg, ResumeMode& resumeMode, MutableHandleValue vp)
+          -> bool { return dbg->fireDebuggerStatement(cx, resumeMode, vp); });
+}
+
+/* static */
+bool DebugAPI::slowPathOnExceptionUnwind(JSContext* cx,
+                                         AbstractFramePtr frame) {
+  // Invoking more JS on an over-recursed stack or after OOM is only going
+  // to result in more of the same error.
+  if (cx->isThrowingOverRecursed() || cx->isThrowingOutOfMemory()) {
+    return true;
+  }
+
+  // The Debugger API mustn't muck with frames from self-hosted scripts.
+  if (frame.hasScript() && frame.script()->selfHosted()) {
+    return true;
+  }
+
+  DebuggerList debuggerList(cx, [](Debugger* dbg) -> bool {
+    return dbg->getHook(Debugger::OnExceptionUnwind);
+  });
+
+  if (!debuggerList.init(cx)) {
+    return false;
+  }
+
+  if (debuggerList.empty()) {
+    return true;
+  }
+
+  // We save and restore the exception once up front to avoid having to do it
+  // for each 'onExceptionUnwind' hook that has been registered, and we also
+  // only do it if the debuggerList contains items in order to avoid extra work.
+  RootedValue exc(cx);
+  RootedSavedFrame stack(cx, cx->getPendingExceptionStack());
+  if (!cx->getPendingException(&exc)) {
+    return false;
+  }
+  cx->clearPendingException();
+
+  bool result = debuggerList.dispatchResumptionHook(
+      cx, frame,
+      [&](Debugger* dbg, ResumeMode& resumeMode,
+          MutableHandleValue vp) -> bool {
+        return dbg->fireExceptionUnwind(cx, exc, resumeMode, vp);
+      });
+  if (!result) {
+    return false;
+  }
+
+  cx->setPendingException(exc, stack);
+  return true;
+}
+
+// TODO: Remove Remove this function when all properties/methods returning a
+///      DebuggerEnvironment have been given a C++ interface (bug 1271649).
+bool Debugger::wrapEnvironment(JSContext* cx, Handle<Env*> env,
+                               MutableHandleValue rval) {
+  if (!env) {
+    rval.setNull();
+    return true;
+  }
+
+  RootedDebuggerEnvironment envobj(cx);
+
+  if (!wrapEnvironment(cx, env, &envobj)) {
+    return false;
+  }
+
+  rval.setObject(*envobj);
+  return true;
+}
+
+bool Debugger::wrapEnvironment(JSContext* cx, Handle<Env*> env,
+                               MutableHandleDebuggerEnvironment result) {
+  MOZ_ASSERT(env);
+
+  // DebuggerEnv should only wrap a debug scope chain obtained (transitively)
+  // from GetDebugEnvironmentFor(Frame|Function).
+  MOZ_ASSERT(!IsSyntacticEnvironment(env));
+
+  DependentAddPtr<EnvironmentWeakMap> p(cx, environments, env);
+  if (p) {
+    result.set(&p->value()->as<DebuggerEnvironment>());
+  } else {
+    // Create a new Debugger.Environment for env.
+    RootedObject proto(
+        cx, &object->getReservedSlot(JSSLOT_DEBUG_ENV_PROTO).toObject());
+    RootedNativeObject debugger(cx, object);
+
+    RootedDebuggerEnvironment envobj(
+        cx, DebuggerEnvironment::create(cx, proto, env, debugger));
+    if (!envobj) {
+      return false;
+    }
+
+    if (!p.add(cx, environments, env, envobj)) {
+      NukeDebuggerWrapper(envobj);
+      return false;
+    }
+
+    result.set(envobj);
+  }
+
+  return true;
+}
+
+bool Debugger::wrapDebuggeeValue(JSContext* cx, MutableHandleValue vp) {
+  cx->check(object.get());
+
+  if (vp.isObject()) {
+    RootedObject obj(cx, &vp.toObject());
+    RootedDebuggerObject dobj(cx);
+
+    if (!wrapDebuggeeObject(cx, obj, &dobj)) {
+      return false;
+    }
+
+    vp.setObject(*dobj);
+  } else if (vp.isMagic()) {
+    RootedPlainObject optObj(cx, NewBuiltinClassInstance<PlainObject>(cx));
+    if (!optObj) {
+      return false;
+    }
+
+    // We handle three sentinel values: missing arguments (overloading
+    // JS_OPTIMIZED_ARGUMENTS), optimized out slots (JS_OPTIMIZED_OUT),
+    // and uninitialized bindings (JS_UNINITIALIZED_LEXICAL).
+    //
+    // Other magic values should not have escaped.
+    PropertyName* name;
+    switch (vp.whyMagic()) {
+      case JS_OPTIMIZED_ARGUMENTS:
+        name = cx->names().missingArguments;
+        break;
+      case JS_OPTIMIZED_OUT:
+        name = cx->names().optimizedOut;
+        break;
+      case JS_UNINITIALIZED_LEXICAL:
+        name = cx->names().uninitialized;
+        break;
+      default:
+        MOZ_CRASH("Unsupported magic value escaped to Debugger");
+    }
+
+    RootedValue trueVal(cx, BooleanValue(true));
+    if (!DefineDataProperty(cx, optObj, name, trueVal)) {
+      return false;
+    }
+
+    vp.setObject(*optObj);
+  } else if (!cx->compartment()->wrap(cx, vp)) {
+    vp.setUndefined();
+    return false;
+  }
+
+  return true;
+}
+
+bool Debugger::wrapNullableDebuggeeObject(JSContext* cx, HandleObject obj,
+                                          MutableHandleDebuggerObject result) {
+  if (!obj) {
+    result.set(nullptr);
+    return true;
+  }
+
+  return wrapDebuggeeObject(cx, obj, result);
+}
+
+bool Debugger::wrapDebuggeeObject(JSContext* cx, HandleObject obj,
+                                  MutableHandleDebuggerObject result) {
+  MOZ_ASSERT(obj);
+
+  DependentAddPtr<ObjectWeakMap> p(cx, objects, obj);
+  if (p) {
+    result.set(&p->value()->as<DebuggerObject>());
+  } else {
+    // Create a new Debugger.Object for obj.
+    RootedNativeObject debugger(cx, object);
+    RootedObject proto(
+        cx, &object->getReservedSlot(JSSLOT_DEBUG_OBJECT_PROTO).toObject());
+    RootedDebuggerObject dobj(cx,
+                              DebuggerObject::create(cx, proto, obj, debugger));
+    if (!dobj) {
+      return false;
+    }
+
+    if (!p.add(cx, objects, obj, dobj)) {
+      NukeDebuggerWrapper(dobj);
+      return false;
+    }
+
+    result.set(dobj);
+  }
+
+  return true;
+}
+
+static DebuggerObject* ToNativeDebuggerObject(JSContext* cx,
+                                              MutableHandleObject obj) {
+  if (!obj->is<DebuggerObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_EXPECTED_TYPE, "Debugger",
+                              "Debugger.Object", obj->getClass()->name);
+    return nullptr;
+  }
+
+  DebuggerObject* ndobj = &obj->as<DebuggerObject>();
+
+  if (!ndobj->isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_DEBUG_PROTO,
+                              "Debugger.Object", "Debugger.Object");
+    return nullptr;
+  }
+
+  return ndobj;
+}
+
+bool Debugger::unwrapDebuggeeObject(JSContext* cx, MutableHandleObject obj) {
+  DebuggerObject* ndobj = ToNativeDebuggerObject(cx, obj);
+  if (!ndobj) {
+    return false;
+  }
+
+  if (ndobj->owner() != Debugger::fromJSObject(object)) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_WRONG_OWNER, "Debugger.Object");
+    return false;
+  }
+
+  obj.set(ndobj->referent());
+  return true;
+}
+
+bool Debugger::unwrapDebuggeeValue(JSContext* cx, MutableHandleValue vp) {
+  cx->check(object.get(), vp);
+  if (vp.isObject()) {
+    RootedObject dobj(cx, &vp.toObject());
+    if (!unwrapDebuggeeObject(cx, &dobj)) {
+      return false;
+    }
+    vp.setObject(*dobj);
+  }
+  return true;
+}
+
+static bool CheckArgCompartment(JSContext* cx, JSObject* obj, JSObject* arg,
+                                const char* methodname, const char* propname) {
+  if (arg->compartment() != obj->compartment()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_COMPARTMENT_MISMATCH, methodname,
+                              propname);
+    return false;
+  }
+  return true;
+}
+
+static bool CheckArgCompartment(JSContext* cx, JSObject* obj, HandleValue v,
+                                const char* methodname, const char* propname) {
+  if (v.isObject()) {
+    return CheckArgCompartment(cx, obj, &v.toObject(), methodname, propname);
+  }
+  return true;
+}
+
+bool Debugger::unwrapPropertyDescriptor(
+    JSContext* cx, HandleObject obj, MutableHandle<PropertyDescriptor> desc) {
+  if (desc.hasValue()) {
+    RootedValue value(cx, desc.value());
+    if (!unwrapDebuggeeValue(cx, &value) ||
+        !CheckArgCompartment(cx, obj, value, "defineProperty", "value")) {
+      return false;
+    }
+    desc.setValue(value);
+  }
+
+  if (desc.hasGetterObject()) {
+    RootedObject get(cx, desc.getterObject());
+    if (get) {
+      if (!unwrapDebuggeeObject(cx, &get)) {
+        return false;
+      }
+      if (!CheckArgCompartment(cx, obj, get, "defineProperty", "get")) {
+        return false;
+      }
+    }
+    desc.setGetterObject(get);
+  }
+
+  if (desc.hasSetterObject()) {
+    RootedObject set(cx, desc.setterObject());
+    if (set) {
+      if (!unwrapDebuggeeObject(cx, &set)) {
+        return false;
+      }
+      if (!CheckArgCompartment(cx, obj, set, "defineProperty", "set")) {
+        return false;
+      }
+    }
+    desc.setSetterObject(set);
+  }
+
+  return true;
+}
+
+/*** Debuggee resumption values and debugger error handling *****************/
+
+static bool GetResumptionProperty(JSContext* cx, HandleObject obj,
+                                  HandlePropertyName name, ResumeMode namedMode,
+                                  ResumeMode& resumeMode, MutableHandleValue vp,
+                                  int* hits) {
+  bool found;
+  if (!HasProperty(cx, obj, name, &found)) {
+    return false;
+  }
+  if (found) {
+    ++*hits;
+    resumeMode = namedMode;
+    if (!GetProperty(cx, obj, obj, name, vp)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool js::ParseResumptionValue(JSContext* cx, HandleValue rval,
+                              ResumeMode& resumeMode, MutableHandleValue vp) {
+  if (rval.isUndefined()) {
+    resumeMode = ResumeMode::Continue;
+    vp.setUndefined();
+    return true;
+  }
+  if (rval.isNull()) {
+    resumeMode = ResumeMode::Terminate;
+    vp.setUndefined();
+    return true;
+  }
+
+  int hits = 0;
+  if (rval.isObject()) {
+    RootedObject obj(cx, &rval.toObject());
+    if (!GetResumptionProperty(cx, obj, cx->names().return_, ResumeMode::Return,
+                               resumeMode, vp, &hits)) {
+      return false;
+    }
+    if (!GetResumptionProperty(cx, obj, cx->names().throw_, ResumeMode::Throw,
+                               resumeMode, vp, &hits)) {
+      return false;
+    }
+  }
+
+  if (hits != 1) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_BAD_RESUMPTION);
+    return false;
+  }
+  return true;
+}
+
+static bool CheckResumptionValue(JSContext* cx, AbstractFramePtr frame,
+                                 jsbytecode* pc, ResumeMode resumeMode,
+                                 MutableHandleValue vp) {
+  // Only forced returns from a frame need to be validated because forced
+  // throw values behave just like debuggee `throw` statements. Since
+  // forced-return is all custom logic within SpiderMonkey itself, we need
+  // our own custom validation for it to conform with what is expected.
+  if (resumeMode != ResumeMode::Return || !frame) {
+    return true;
+  }
+
+  // This replicates the ECMA spec's behavior for [[Construct]] in derived
+  // class constructors (section 9.2.2 of ECMA262-2020), where returning a
+  // non-undefined primitive causes an exception tobe thrown.
+  if (frame.debuggerNeedsCheckPrimitiveReturn() && vp.isPrimitive()) {
+    if (!vp.isUndefined()) {
+      ReportValueError(cx, JSMSG_BAD_DERIVED_RETURN, JSDVG_IGNORE_STACK, vp,
+                       nullptr);
+      return false;
+    }
+
+    RootedValue thisv(cx);
+    {
+      AutoRealm ar(cx, frame.environmentChain());
+      if (!GetThisValueForDebuggerFrameMaybeOptimizedOut(cx, frame, pc,
+                                                         &thisv)) {
+        return false;
+      }
+    }
+
+    if (thisv.isMagic(JS_UNINITIALIZED_LEXICAL)) {
+      return ThrowUninitializedThis(cx);
+    }
+    MOZ_ASSERT(!thisv.isMagic());
+
+    if (!cx->compartment()->wrap(cx, &thisv)) {
+      return false;
+    }
+    vp.set(thisv);
+  }
+
+  // Check for forcing return from a generator before the initial yield. This
+  // is not supported because some engine-internal code assumes a call to a
+  // generator will return a GeneratorObject; see bug 1477084.
+  if (frame.isFunctionFrame() && frame.callee()->isGenerator()) {
+    Rooted<AbstractGeneratorObject*> genObj(cx);
+    {
+      AutoRealm ar(cx, frame.callee());
+      genObj = GetGeneratorObjectForFrame(cx, frame);
+    }
+
+    if (!genObj || genObj->isBeforeInitialYield()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_FORCED_RETURN_DISALLOWED);
+      return false;
+    }
+  }
+
+  return true;
+}
+
+// Last-minute sanity adjustments to resumption.
+//
+// This is called last, as we leave the debugger. It must happen outside the
+// control of the uncaughtExceptionHook, because this code assumes we won't
+// change our minds and continue execution--we must not close the generator
+// object unless we're really going to force-return.
+static MOZ_MUST_USE bool AdjustGeneratorResumptionValue(JSContext* cx,
+                                                        AbstractFramePtr frame,
+                                                        ResumeMode& resumeMode,
+                                                        MutableHandleValue vp) {
+  if (resumeMode != ResumeMode::Return && resumeMode != ResumeMode::Throw) {
+    return true;
+  }
+  if (!frame || !frame.isFunctionFrame()) {
+    return true;
+  }
+
+  // Treat `{return: <value>}` like a `return` statement. Simulate what the
+  // debuggee would do for an ordinary `return` statement, using a few bytecode
+  // instructions. It's simpler to do the work manually than to count on that
+  // bytecode sequence existing in the debuggee, somehow jump to it, and then
+  // avoid re-entering the debugger from it.
+  //
+  // Similarly treat `{throw: <value>}` like a `throw` statement.
+  if (frame.callee()->isGenerator()) {
+    // Throw doesn't require any special processing for (async) generators.
+    if (resumeMode == ResumeMode::Throw) {
+      return true;
+    }
+
+    // Forcing return from a (possibly async) generator.
+    Rooted<AbstractGeneratorObject*> genObj(
+        cx, GetGeneratorObjectForFrame(cx, frame));
+
+    // We already went through CheckResumptionValue, which would have replaced
+    // this invalid resumption value with an error if we were trying to force
+    // return before the initial yield.
+    MOZ_RELEASE_ASSERT(genObj && !genObj->isBeforeInitialYield());
+
+    // 1.  `return <value>` creates and returns a new object,
+    //     `{value: <value>, done: true}`.
+    //
+    // For non-async generators, the iterator result object is created in
+    // bytecode, so we have to simulate that here. For async generators, our
+    // C++ implementation of AsyncGeneratorResolve will do this. So don't do it
+    // twice:
+    if (!genObj->is<AsyncGeneratorObject>()) {
+      PlainObject* pair = CreateIterResultObject(cx, vp, true);
+      if (!pair) {
+        return false;
+      }
+      vp.setObject(*pair);
+    }
+
+    // 2.  The generator must be closed.
+    genObj->setClosed();
+
+    // Async generators have additionally bookkeeping which must be adjusted
+    // when switching over to the closed state.
+    if (genObj->is<AsyncGeneratorObject>()) {
+      genObj->as<AsyncGeneratorObject>().setCompleted();
+    }
+  } else if (frame.callee()->isAsync()) {
+    if (AbstractGeneratorObject* genObj =
+            GetGeneratorObjectForFrame(cx, frame)) {
+      // Throw doesn't require any special processing for async functions when
+      // the internal generator object is already present.
+      if (resumeMode == ResumeMode::Throw) {
+        return true;
+      }
+
+      Rooted<AsyncFunctionGeneratorObject*> asyncGenObj(
+          cx, &genObj->as<AsyncFunctionGeneratorObject>());
+
+      // 1.  `return <value>` fulfills and returns the async function's promise.
+      Rooted<PromiseObject*> promise(cx, asyncGenObj->promise());
+      if (promise->state() == JS::PromiseState::Pending) {
+        if (!AsyncFunctionResolve(cx, asyncGenObj, vp,
+                                  AsyncFunctionResolveKind::Fulfill)) {
+          return false;
+        }
+      }
+      vp.setObject(*promise);
+
+      // 2.  The generator must be closed.
+      asyncGenObj->setClosed();
+    } else {
+      // We're before entering the actual function code.
+
+      // 1.  `throw <value>` creates a promise rejected with the value *vp.
+      // 1.  `return <value>` creates a promise resolved with the value *vp.
+      JSObject* promise = resumeMode == ResumeMode::Throw
+                              ? PromiseObject::unforgeableReject(cx, vp)
+                              : PromiseObject::unforgeableResolve(cx, vp);
+      if (!promise) {
+        return false;
+      }
+      vp.setObject(*promise);
+
+      // 2.  Return normally in both cases.
+      resumeMode = ResumeMode::Return;
+    }
+  }
+
+  return true;
+}
+
+bool Debugger::processParsedHandlerResult(JSContext* cx, AbstractFramePtr frame,
+                                          jsbytecode* pc, bool success,
+                                          ResumeMode resumeMode,
+                                          HandleValue value,
+                                          ResumeMode& resultMode,
+                                          MutableHandleValue vp) {
+  RootedValue rootValue(cx, value);
+  if (!success || !prepareResumption(cx, frame, pc, resumeMode, &rootValue)) {
+    RootedValue exceptionRv(cx);
+    if (!callUncaughtExceptionHandler(cx, &exceptionRv) ||
+        !ParseResumptionValue(cx, exceptionRv, resumeMode, &rootValue) ||
+        !prepareResumption(cx, frame, pc, resumeMode, &rootValue)) {
+      return false;
+    }
+  }
+
+  // Since debugger hooks accumulate into the same final value handle, we
+  // use that to throw if multiple hooks try to set a resumption value.
+  if (resumeMode != ResumeMode::Continue) {
+    if (resultMode != ResumeMode::Continue) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_RESUMPTION_CONFLICT);
+      return false;
+    }
+
+    vp.set(rootValue);
+    resultMode = resumeMode;
+  }
+
+  return true;
+}
+
+bool Debugger::processHandlerResult(JSContext* cx, bool success, HandleValue rv,
+                                    AbstractFramePtr frame, jsbytecode* pc,
+                                    ResumeMode& resultMode,
+                                    MutableHandleValue vp) {
+  ResumeMode resumeMode = ResumeMode::Continue;
+  RootedValue value(cx);
+  if (success) {
+    success = ParseResumptionValue(cx, rv, resumeMode, &value);
+  }
+  return processParsedHandlerResult(cx, frame, pc, success, resumeMode, value,
+                                    resultMode, vp);
+}
+
+bool Debugger::prepareResumption(JSContext* cx, AbstractFramePtr frame,
+                                 jsbytecode* pc, ResumeMode& resumeMode,
+                                 MutableHandleValue vp) {
+  return unwrapDebuggeeValue(cx, vp) &&
+         CheckResumptionValue(cx, frame, pc, resumeMode, vp);
+}
+
+bool Debugger::callUncaughtExceptionHandler(JSContext* cx,
+                                            MutableHandleValue vp) {
+  // Uncaught exceptions arise from Debugger code, and so we must already be in
+  // an NX section. This also establishes that we are already within the scope
+  // of an AutoDebuggerJobQueueInterruption object.
+  MOZ_ASSERT(EnterDebuggeeNoExecute::isLockedInStack(cx, *this));
+
+  if (cx->isExceptionPending() && uncaughtExceptionHook) {
+    RootedValue exc(cx);
+    if (!cx->getPendingException(&exc)) {
+      return false;
+    }
+    cx->clearPendingException();
+
+    RootedValue fval(cx, ObjectValue(*uncaughtExceptionHook));
+    if (js::Call(cx, fval, object, exc, vp)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool Debugger::handleUncaughtException(JSContext* cx) {
+  RootedValue rv(cx);
+
+  return callUncaughtExceptionHandler(cx, &rv);
+}
+
+void Debugger::reportUncaughtException(JSContext* cx) {
+  // Uncaught exceptions arise from Debugger code, and so we must already be
+  // in an NX section.
+  MOZ_ASSERT(EnterDebuggeeNoExecute::isLockedInStack(cx, *this));
+
+  if (cx->isExceptionPending()) {
+    // We want to report the pending exception, but we want to let the
+    // embedding handle it however it wants to.  So pretend like we're
+    // starting a new script execution on our current compartment (which
+    // is the debugger compartment, so reported errors won't get
+    // reported to various onerror handlers in debuggees) and as part of
+    // that "execution" simply throw our exception so the embedding can
+    // deal.
+    RootedValue exn(cx);
+    if (cx->getPendingException(&exn)) {
+      // Clear the exception, because ReportErrorToGlobal will assert that
+      // we don't have one.
+      cx->clearPendingException();
+      ReportErrorToGlobal(cx, cx->global(), exn);
+    }
+
+    // And if not, or if PrepareScriptEnvironmentAndInvoke somehow left an
+    // exception on cx (which it totally shouldn't do), just give up.
+    cx->clearPendingException();
+  }
+}
+
+/*** Debuggee completion values *********************************************/
+
+/* static */
+Completion Completion::fromJSResult(JSContext* cx, bool ok, const Value& rv) {
+  MOZ_ASSERT_IF(ok, !cx->isExceptionPending());
+
+  if (ok) {
+    return Completion(Return(rv));
+  }
+
+  if (!cx->isExceptionPending()) {
+    return Completion(Terminate());
+  }
+
+  RootedValue exception(cx);
+  RootedSavedFrame stack(cx, cx->getPendingExceptionStack());
+  bool getSucceeded = cx->getPendingException(&exception);
+  cx->clearPendingException();
+  if (!getSucceeded) {
+    return Completion(Terminate());
+  }
+
+  return Completion(Throw(exception, stack));
+}
+
+/* static */
+Completion Completion::fromJSFramePop(JSContext* cx, AbstractFramePtr frame,
+                                      const jsbytecode* pc, bool ok) {
+  // Only Wasm frames get a null pc.
+  MOZ_ASSERT_IF(!frame.isWasmDebugFrame(), pc);
+
+  // If this isn't a generator suspension, then that's already handled above.
+  if (!ok || !frame.isGeneratorFrame()) {
+    return fromJSResult(cx, ok, frame.returnValue());
+  }
+
+  // A generator is being suspended or returning.
+
+  // Since generators are never wasm, we can assume pc is not nullptr, and
+  // that analyzing bytecode is meaningful.
+  MOZ_ASSERT(!frame.isWasmDebugFrame());
+
+  // If we're leaving successfully at a yield opcode, we're probably
+  // suspending; the `isClosed()` check detects a debugger forced return from
+  // an `onStep` handler, which looks almost the same.
+  //
+  // GetGeneratorObjectForFrame can return nullptr even when a generator
+  // object does exist, if the frame is paused between the Generator and
+  // SetAliasedVar opcodes. But by checking the opcode first we eliminate that
+  // possibility, so it's fine to call genObj->isClosed().
+  Rooted<AbstractGeneratorObject*> generatorObj(
+      cx, GetGeneratorObjectForFrame(cx, frame));
+  switch (JSOp(*pc)) {
+    case JSOp::InitialYield:
+      MOZ_ASSERT(!generatorObj->isClosed());
+      return Completion(InitialYield(generatorObj));
+
+    case JSOp::Yield:
+      MOZ_ASSERT(!generatorObj->isClosed());
+      return Completion(Yield(generatorObj, frame.returnValue()));
+
+    case JSOp::Await:
+      MOZ_ASSERT(!generatorObj->isClosed());
+      return Completion(Await(generatorObj, frame.returnValue()));
+
+    default:
+      return Completion(Return(frame.returnValue()));
+  }
+}
+
+void Completion::trace(JSTracer* trc) {
+  variant.match([=](auto& var) { var.trace(trc); });
+}
+
+struct MOZ_STACK_CLASS Completion::BuildValueMatcher {
+  JSContext* cx;
+  Debugger* dbg;
+  MutableHandleValue result;
+
+  BuildValueMatcher(JSContext* cx, Debugger* dbg, MutableHandleValue result)
+      : cx(cx), dbg(dbg), result(result) {
+    cx->check(dbg->toJSObject());
+  }
+
+  bool operator()(const Completion::Return& ret) {
+    RootedNativeObject obj(cx, newObject());
+    RootedValue retval(cx, ret.value);
+    if (!obj || !wrap(&retval) || !add(obj, cx->names().return_, retval)) {
+      return false;
+    }
+    result.setObject(*obj);
+    return true;
+  }
+
+  bool operator()(const Completion::Throw& thr) {
+    RootedNativeObject obj(cx, newObject());
+    RootedValue exc(cx, thr.exception);
+    if (!obj || !wrap(&exc) || !add(obj, cx->names().throw_, exc)) {
+      return false;
+    }
+    if (thr.stack) {
+      RootedValue stack(cx, ObjectValue(*thr.stack));
+      if (!wrapStack(&stack) || !add(obj, cx->names().stack, stack)) {
+        return false;
+      }
+    }
+    result.setObject(*obj);
+    return true;
+  }
+
+  bool operator()(const Completion::Terminate& term) {
+    result.setNull();
+    return true;
+  }
+
+  bool operator()(const Completion::InitialYield& initialYield) {
+    RootedNativeObject obj(cx, newObject());
+    RootedValue gen(cx, ObjectValue(*initialYield.generatorObject));
+    if (!obj || !wrap(&gen) || !add(obj, cx->names().return_, gen) ||
+        !add(obj, cx->names().yield, TrueHandleValue) ||
+        !add(obj, cx->names().initial, TrueHandleValue)) {
+      return false;
+    }
+    result.setObject(*obj);
+    return true;
+  }
+
+  bool operator()(const Completion::Yield& yield) {
+    RootedNativeObject obj(cx, newObject());
+    RootedValue iteratorResult(cx, yield.iteratorResult);
+    if (!obj || !wrap(&iteratorResult) ||
+        !add(obj, cx->names().return_, iteratorResult) ||
+        !add(obj, cx->names().yield, TrueHandleValue)) {
+      return false;
+    }
+    result.setObject(*obj);
+    return true;
+  }
+
+  bool operator()(const Completion::Await& await) {
+    RootedNativeObject obj(cx, newObject());
+    RootedValue awaitee(cx, await.awaitee);
+    if (!obj || !wrap(&awaitee) || !add(obj, cx->names().return_, awaitee) ||
+        !add(obj, cx->names().await, TrueHandleValue)) {
+      return false;
+    }
+    result.setObject(*obj);
+    return true;
+  }
+
+ private:
+  NativeObject* newObject() const {
+    return NewBuiltinClassInstance<PlainObject>(cx);
+  }
+
+  bool add(HandleNativeObject obj, PropertyName* name,
+           HandleValue value) const {
+    return NativeDefineDataProperty(cx, obj, name, value, JSPROP_ENUMERATE);
+  }
+
+  bool wrap(MutableHandleValue v) const {
+    return dbg->wrapDebuggeeValue(cx, v);
+  }
+
+  // Saved stacks are wrapped for direct consumption by debugger code.
+  bool wrapStack(MutableHandleValue stack) const {
+    return cx->compartment()->wrap(cx, stack);
+  }
+};
+
+bool Completion::buildCompletionValue(JSContext* cx, Debugger* dbg,
+                                      MutableHandleValue result) const {
+  return variant.match(BuildValueMatcher(cx, dbg, result));
+}
+
+void Completion::updateFromHookResult(ResumeMode resumeMode,
+                                      HandleValue value) {
+  switch (resumeMode) {
+    case ResumeMode::Continue:
+      // No change to how we'll resume.
+      break;
+
+    case ResumeMode::Throw:
+      // Since this is a new exception, the stack for the old one may not apply.
+      // If we extend resumption values to specify stacks, we could revisit
+      // this.
+      variant = Variant(Throw(value, nullptr));
+      break;
+
+    case ResumeMode::Terminate:
+      variant = Variant(Terminate());
+      break;
+
+    case ResumeMode::Return:
+      variant = Variant(Return(value));
+      break;
+
+    default:
+      MOZ_CRASH("invalid resumeMode value");
+  }
+}
+
+struct MOZ_STACK_CLASS Completion::ToResumeModeMatcher {
+  MutableHandleValue value;
+  MutableHandleSavedFrame exnStack;
+  ToResumeModeMatcher(MutableHandleValue value,
+                      MutableHandleSavedFrame exnStack)
+      : value(value), exnStack(exnStack) {}
+
+  ResumeMode operator()(const Return& ret) {
+    value.set(ret.value);
+    return ResumeMode::Return;
+  }
+
+  ResumeMode operator()(const Throw& thr) {
+    value.set(thr.exception);
+    exnStack.set(thr.stack);
+    return ResumeMode::Throw;
+  }
+
+  ResumeMode operator()(const Terminate& term) {
+    value.setUndefined();
+    return ResumeMode::Terminate;
+  }
+
+  ResumeMode operator()(const InitialYield& initialYield) {
+    value.setObject(*initialYield.generatorObject);
+    return ResumeMode::Return;
+  }
+
+  ResumeMode operator()(const Yield& yield) {
+    value.set(yield.iteratorResult);
+    return ResumeMode::Return;
+  }
+
+  ResumeMode operator()(const Await& await) {
+    value.set(await.awaitee);
+    return ResumeMode::Return;
+  }
+};
+
+void Completion::toResumeMode(ResumeMode& resumeMode, MutableHandleValue value,
+                              MutableHandleSavedFrame exnStack) const {
+  resumeMode = variant.match(ToResumeModeMatcher(value, exnStack));
+}
+
+/*** Firing debugger hooks **************************************************/
+
+static bool CallMethodIfPresent(JSContext* cx, HandleObject obj,
+                                const char* name, size_t argc, Value* argv,
+                                MutableHandleValue rval) {
+  rval.setUndefined();
+  JSAtom* atom = Atomize(cx, name, strlen(name));
+  if (!atom) {
+    return false;
+  }
+
+  RootedId id(cx, AtomToId(atom));
+  RootedValue fval(cx);
+  if (!GetProperty(cx, obj, obj, id, &fval)) {
+    return false;
+  }
+
+  if (!IsCallable(fval)) {
+    return true;
+  }
+
+  InvokeArgs args(cx);
+  if (!args.init(cx, argc)) {
+    return false;
+  }
+
+  for (size_t i = 0; i < argc; i++) {
+    args[i].set(argv[i]);
+  }
+
+  rval.setObject(*obj);  // overwritten by successful Call
+  return js::Call(cx, fval, rval, args, rval);
+}
+
+bool Debugger::fireDebuggerStatement(JSContext* cx, ResumeMode& resumeMode,
+                                     MutableHandleValue vp) {
+  RootedObject hook(cx, getHook(OnDebuggerStatement));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  ScriptFrameIter iter(cx);
+  RootedValue scriptFrame(cx);
+  if (!getFrame(cx, iter, &scriptFrame)) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue rv(cx);
+  bool ok = js::Call(cx, fval, object, scriptFrame, &rv);
+  return processHandlerResult(cx, ok, rv, iter.abstractFramePtr(), iter.pc(),
+                              resumeMode, vp);
+}
+
+bool Debugger::fireExceptionUnwind(JSContext* cx, HandleValue exc,
+                                   ResumeMode& resumeMode,
+                                   MutableHandleValue vp) {
+  RootedObject hook(cx, getHook(OnExceptionUnwind));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  RootedValue scriptFrame(cx);
+  RootedValue wrappedExc(cx, exc);
+
+  FrameIter iter(cx);
+  if (!getFrame(cx, iter, &scriptFrame) ||
+      !wrapDebuggeeValue(cx, &wrappedExc)) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue rv(cx);
+  bool ok = js::Call(cx, fval, object, scriptFrame, wrappedExc, &rv);
+  return processHandlerResult(cx, ok, rv, iter.abstractFramePtr(), iter.pc(),
+                              resumeMode, vp);
+}
+
+bool Debugger::fireEnterFrame(JSContext* cx, ResumeMode& resumeMode,
+                              MutableHandleValue vp) {
+  RootedObject hook(cx, getHook(OnEnterFrame));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  RootedValue scriptFrame(cx);
+
+  FrameIter iter(cx);
+
+#if DEBUG
+  // Assert that the hook won't be able to re-enter the generator.
+  if (iter.hasScript() && JSOp(*iter.pc()) == JSOp::AfterYield) {
+    AutoRealm ar(cx, iter.script());
+    auto* genObj = GetGeneratorObjectForFrame(cx, iter.abstractFramePtr());
+    MOZ_ASSERT(genObj->isRunning());
+  }
+#endif
+
+  if (!getFrame(cx, iter, &scriptFrame)) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue rv(cx);
+  bool ok = js::Call(cx, fval, object, scriptFrame, &rv);
+
+  return processHandlerResult(cx, ok, rv, iter.abstractFramePtr(), iter.pc(),
+                              resumeMode, vp);
+}
+
+bool Debugger::fireNativeCall(JSContext* cx, const CallArgs& args,
+                              CallReason reason, ResumeMode& resumeMode,
+                              MutableHandleValue vp) {
+  RootedObject hook(cx, getHook(OnNativeCall));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue calleeval(cx, args.calleev());
+  if (!wrapDebuggeeValue(cx, &calleeval)) {
+    return false;
+  }
+
+  JSAtom* reasonAtom = nullptr;
+  switch (reason) {
+    case CallReason::Call:
+      reasonAtom = cx->names().call;
+      break;
+    case CallReason::Getter:
+      reasonAtom = cx->names().get;
+      break;
+    case CallReason::Setter:
+      reasonAtom = cx->names().set;
+      break;
+  }
+  cx->markAtom(reasonAtom);
+
+  RootedValue reasonval(cx, StringValue(reasonAtom));
+
+  RootedValue rv(cx);
+  bool ok = js::Call(cx, fval, object, calleeval, reasonval, &rv);
+
+  return processHandlerResult(cx, ok, rv, NullFramePtr(), nullptr, resumeMode,
+                              vp);
+}
+
+bool Debugger::fireNewScript(JSContext* cx,
+                             Handle<DebuggerScriptReferent> scriptReferent) {
+  RootedObject hook(cx, getHook(OnNewScript));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  JSObject* dsobj = wrapVariantReferent(cx, scriptReferent);
+  if (!dsobj) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue dsval(cx, ObjectValue(*dsobj));
+  RootedValue rv(cx);
+  return js::Call(cx, fval, object, dsval, &rv) || handleUncaughtException(cx);
+}
+
+bool Debugger::fireOnGarbageCollectionHook(
+    JSContext* cx, const JS::dbg::GarbageCollectionEvent::Ptr& gcData) {
+  MOZ_ASSERT(observedGC(gcData->majorGCNumber()));
+  observedGCs.remove(gcData->majorGCNumber());
+
+  RootedObject hook(cx, getHook(OnGarbageCollection));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  JSObject* dataObj = gcData->toJSObject(cx);
+  if (!dataObj) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*hook));
+  RootedValue dataVal(cx, ObjectValue(*dataObj));
+  RootedValue rv(cx);
+  return js::Call(cx, fval, object, dataVal, &rv) ||
+         handleUncaughtException(cx);
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */,
+          typename FireHookFun /* bool (Debugger*) */>
+/* static */
+void Debugger::dispatchQuietHook(JSContext* cx, HookIsEnabledFun hookIsEnabled,
+                                 FireHookFun fireHook) {
+  DebuggerList<HookIsEnabledFun> debuggerList(cx, hookIsEnabled);
+
+  if (!debuggerList.init(cx)) {
+    // init may fail due to OOM. This OOM is not handlable at the
+    // callsites of dispatchQuietHook in the engine.
+    cx->clearPendingException();
+    return;
+  }
+
+  debuggerList.dispatchQuietHook(cx, fireHook);
+}
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */, typename FireHookFun /* bool (Debugger*, ResumeMode&, MutableHandleValue vp) */>
+/* static */
+bool Debugger::dispatchResumptionHook(JSContext* cx, AbstractFramePtr frame,
+                                      HookIsEnabledFun hookIsEnabled,
+                                      FireHookFun fireHook) {
+  DebuggerList<HookIsEnabledFun> debuggerList(cx, hookIsEnabled);
+
+  if (!debuggerList.init(cx)) {
+    return false;
+  }
+
+  return debuggerList.dispatchResumptionHook(cx, frame, fireHook);
+}
+
+// Maximum length for source URLs that can be remembered.
+static const size_t SourceURLMaxLength = 1024;
+
+// Maximum number of source URLs that can be remembered in a realm.
+static const size_t SourceURLRealmLimit = 100;
+
+static bool RememberSourceURL(JSContext* cx, HandleScript script) {
+  cx->check(script);
+
+  // Sources introduced dynamically are not remembered.
+  if (script->sourceObject()->unwrappedIntroductionScript()) {
+    return true;
+  }
+
+  const char* filename = script->filename();
+  if (!filename ||
+      strnlen(filename, SourceURLMaxLength + 1) > SourceURLMaxLength) {
+    return true;
+  }
+
+  RootedObject holder(cx, script->global().getSourceURLsHolder());
+  if (!holder) {
+    holder = NewDenseEmptyArray(cx);
+    if (!holder) {
+      return false;
+    }
+    script->global().setSourceURLsHolder(holder);
+  }
+
+  if (holder->as<ArrayObject>().length() >= SourceURLRealmLimit) {
+    return true;
+  }
+
+  RootedString filenameString(cx, JS_AtomizeString(cx, filename));
+  if (!filenameString) {
+    return false;
+  }
+
+  // The source URLs holder never escapes to script, so we can treat it as a
+  // newborn array for the purpose of adding elements.
+  return NewbornArrayPush(cx, holder, StringValue(filenameString));
+}
+
+void DebugAPI::onNewScript(JSContext* cx, HandleScript script) {
+  if (!script->realm()->isDebuggee()) {
+    // Remember the URLs associated with scripts in non-system realms,
+    // in case the debugger is attached later.
+    if (!script->realm()->isSystem()) {
+      if (!RememberSourceURL(cx, script)) {
+        cx->clearPendingException();
+      }
+    }
+    return;
+  }
+
+  Debugger::dispatchQuietHook(
+      cx,
+      [script](Debugger* dbg) -> bool {
+        return dbg->observesNewScript() && dbg->observesScript(script);
+      },
+      [&](Debugger* dbg) -> bool {
+        BaseScript* base = script.get();
+        Rooted<DebuggerScriptReferent> scriptReferent(cx, base);
+        return dbg->fireNewScript(cx, scriptReferent);
+      });
+}
+
+void DebugAPI::slowPathOnNewWasmInstance(
+    JSContext* cx, Handle<WasmInstanceObject*> wasmInstance) {
+  Debugger::dispatchQuietHook(
+      cx,
+      [wasmInstance](Debugger* dbg) -> bool {
+        return dbg->observesNewScript() &&
+               dbg->observesGlobal(&wasmInstance->global());
+      },
+      [&](Debugger* dbg) -> bool {
+        Rooted<DebuggerScriptReferent> scriptReferent(cx, wasmInstance.get());
+        return dbg->fireNewScript(cx, scriptReferent);
+      });
+}
+
+/* static */
+bool DebugAPI::onTrap(JSContext* cx) {
+  FrameIter iter(cx);
+  JS::AutoSaveExceptionState savedExc(cx);
+  Rooted<GlobalObject*> global(cx);
+  BreakpointSite* site;
+  bool isJS;       // true when iter.hasScript(), false when iter.isWasm()
+  jsbytecode* pc;  // valid when isJS == true
+  uint32_t bytecodeOffset;  // valid when isJS == false
+  if (iter.hasScript()) {
+    RootedScript script(cx, iter.script());
+    MOZ_ASSERT(script->isDebuggee());
+    global.set(&script->global());
+    isJS = true;
+    pc = iter.pc();
+    bytecodeOffset = 0;
+    site = DebugScript::getBreakpointSite(script, pc);
+  } else {
+    MOZ_ASSERT(iter.isWasm());
+    global.set(&iter.wasmInstance()->object()->global());
+    isJS = false;
+    pc = nullptr;
+    bytecodeOffset = iter.wasmBytecodeOffset();
+    site = iter.wasmInstance()->debug().getBreakpointSite(bytecodeOffset);
+  }
+
+  // Build list of breakpoint handlers.
+  //
+  // This does not need to be rooted: since the JSScript/WasmInstance is on the
+  // stack, the Breakpoints will not be GC'd. However, they may be deleted, and
+  // we check for that case below.
+  Vector<Breakpoint*> triggered(cx);
+  for (Breakpoint* bp = site->firstBreakpoint(); bp; bp = bp->nextInSite()) {
+    if (!triggered.append(bp)) {
+      return false;
+    }
+  }
+
+  ResumeMode resumeMode = ResumeMode::Continue;
+  RootedValue rval(cx);
+
+  if (triggered.length() > 0) {
+    // Preserve the debuggee's microtask event queue while we run the hooks, so
+    // the debugger's microtask checkpoints don't run from the debuggee's
+    // microtasks, and vice versa.
+    JS::AutoDebuggerJobQueueInterruption adjqi;
+    if (!adjqi.init(cx)) {
+      return false;
+    }
+
+    for (Breakpoint* bp : triggered) {
+      // Handlers can clear breakpoints. Check that bp still exists.
+      if (!site || !site->hasBreakpoint(bp)) {
+        continue;
+      }
+
+      // There are two reasons we have to check whether dbg is debugging
+      // global.
+      //
+      // One is just that one breakpoint handler can disable other Debuggers
+      // or remove debuggees.
+      //
+      // The other has to do with non-compile-and-go scripts, which have no
+      // specific global--until they are executed. Only now do we know which
+      // global the script is running against.
+      Debugger* dbg = bp->debugger;
+      if (dbg->debuggees.has(global)) {
+        EnterDebuggeeNoExecute nx(cx, *dbg, adjqi);
+
+        bool result = dbg->enterDebuggerHook(cx, [&]() -> bool {
+          RootedValue scriptFrame(cx);
+          if (!dbg->getFrame(cx, iter, &scriptFrame)) {
+            return false;
+          }
+
+          // Re-wrap the breakpoint's handler for the Debugger's compartment.
+          // When the handler and the Debugger are in the same compartment (the
+          // usual case), this actually unwraps it, but there's no requirement
+          // that they be in the same compartment, so we can't be sure.
+          Rooted<JSObject*> handler(cx, bp->handler);
+          if (!cx->compartment()->wrap(cx, &handler)) {
+            return false;
+          }
+
+          RootedValue rv(cx);
+          bool ok = CallMethodIfPresent(cx, handler, "hit", 1,
+                                        scriptFrame.address(), &rv);
+
+          return dbg->processHandlerResult(cx, ok, rv, iter.abstractFramePtr(),
+                                           iter.pc(), resumeMode, &rval);
+        });
+        adjqi.runJobs();
+
+        if (!result) {
+          return false;
+        }
+
+        // Calling JS code invalidates site. Reload it.
+        if (isJS) {
+          site = DebugScript::getBreakpointSite(iter.script(), pc);
+        } else {
+          site = iter.wasmInstance()->debug().getBreakpointSite(bytecodeOffset);
+        }
+      }
+    }
+  }
+
+  if (!ApplyFrameResumeMode(cx, iter.abstractFramePtr(), resumeMode, rval)) {
+    savedExc.drop();
+    return false;
+  }
+  return true;
+}
+
+/* static */
+bool DebugAPI::onSingleStep(JSContext* cx) {
+  FrameIter iter(cx);
+
+  // We may be stepping over a JSOp::Exception, that pushes the context's
+  // pending exception for a 'catch' clause to handle. Don't let the onStep
+  // handlers mess with that (other than by returning a resumption value).
+  JS::AutoSaveExceptionState savedExc(cx);
+
+  // Build list of Debugger.Frame instances referring to this frame with
+  // onStep handlers.
+  Rooted<Debugger::DebuggerFrameVector> frames(
+      cx, Debugger::DebuggerFrameVector(cx));
+  if (!Debugger::getDebuggerFrames(iter.abstractFramePtr(), &frames)) {
+    return false;
+  }
+
+#ifdef DEBUG
+  // Validate the single-step count on this frame's script, to ensure that
+  // we're not receiving traps we didn't ask for. Even when frames is
+  // non-empty (and thus we know this trap was requested), do the check
+  // anyway, to make sure the count has the correct non-zero value.
+  //
+  // The converse --- ensuring that we do receive traps when we should --- can
+  // be done with unit tests.
+  if (iter.hasScript()) {
+    uint32_t liveStepperCount = 0;
+    uint32_t suspendedStepperCount = 0;
+    JSScript* trappingScript = iter.script();
+    for (Realm::DebuggerVectorEntry& entry : cx->global()->getDebuggers()) {
+      Debugger* dbg = entry.dbg;
+      for (Debugger::FrameMap::Range r = dbg->frames.all(); !r.empty();
+           r.popFront()) {
+        AbstractFramePtr frame = r.front().key();
+        NativeObject* frameobj = r.front().value();
+        if (frame.isWasmDebugFrame()) {
+          continue;
+        }
+        if (frame.script() == trappingScript &&
+            !frameobj->getReservedSlot(DebuggerFrame::ONSTEP_HANDLER_SLOT)
+                 .isUndefined()) {
+          liveStepperCount++;
+        }
+      }
+
+      // Also count hooks set on suspended generator frames.
+      for (Debugger::GeneratorWeakMap::Range r = dbg->generatorFrames.all();
+           !r.empty(); r.popFront()) {
+        AbstractGeneratorObject& genObj = *r.front().key();
+        DebuggerFrame& frameObj = *r.front().value();
+        MOZ_ASSERT(&frameObj.unwrappedGenerator() == &genObj);
+
+        // Live Debugger.Frames were already counted in dbg->frames loop.
+        if (frameObj.isOnStack()) {
+          continue;
+        }
+
+        // A closed generator no longer has a callee so it will not be able to
+        // compare with the trappingScript.
+        if (genObj.isClosed()) {
+          continue;
+        }
+
+        // If a frame isn't live, but it has an entry in generatorFrames,
+        // it had better be suspended.
+        MOZ_ASSERT(genObj.isSuspended());
+
+        if (genObj.callee().hasBaseScript() &&
+            genObj.callee().baseScript() == trappingScript &&
+            !frameObj.getReservedSlot(DebuggerFrame::ONSTEP_HANDLER_SLOT)
+                 .isUndefined()) {
+          suspendedStepperCount++;
+        }
+      }
+    }
+
+    MOZ_ASSERT(liveStepperCount + suspendedStepperCount ==
+               DebugScript::getStepperCount(trappingScript));
+  }
+#endif
+
+  RootedValue rval(cx);
+  ResumeMode resumeMode = ResumeMode::Continue;
+
+  if (frames.length() > 0) {
+    // Preserve the debuggee's microtask event queue while we run the hooks, so
+    // the debugger's microtask checkpoints don't run from the debuggee's
+    // microtasks, and vice versa.
+    JS::AutoDebuggerJobQueueInterruption adjqi;
+    if (!adjqi.init(cx)) {
+      return false;
+    }
+
+    // Call onStep for frames that have the handler set.
+    for (size_t i = 0; i < frames.length(); i++) {
+      HandleDebuggerFrame frame = frames[i];
+      OnStepHandler* handler = frame->onStepHandler();
+      if (!handler) {
+        continue;
+      }
+
+      Debugger* dbg = frame->owner();
+      EnterDebuggeeNoExecute nx(cx, *dbg, adjqi);
+
+      bool result = dbg->enterDebuggerHook(cx, [&]() -> bool {
+        ResumeMode nextResumeMode = ResumeMode::Continue;
+        RootedValue nextValue(cx);
+
+        bool success = handler->onStep(cx, frame, nextResumeMode, &nextValue);
+        return dbg->processParsedHandlerResult(
+            cx, iter.abstractFramePtr(), iter.pc(), success, nextResumeMode,
+            nextValue, resumeMode, &rval);
+      });
+      adjqi.runJobs();
+
+      if (!result) {
+        return false;
+      }
+    }
+  }
+
+  if (!ApplyFrameResumeMode(cx, iter.abstractFramePtr(), resumeMode, rval)) {
+    savedExc.drop();
+    return false;
+  }
+  return true;
+}
+
+bool Debugger::fireNewGlobalObject(JSContext* cx,
+                                   Handle<GlobalObject*> global) {
+  RootedObject hook(cx, getHook(OnNewGlobalObject));
+  MOZ_ASSERT(hook);
+  MOZ_ASSERT(hook->isCallable());
+
+  RootedValue wrappedGlobal(cx, ObjectValue(*global));
+  if (!wrapDebuggeeValue(cx, &wrappedGlobal)) {
+    return false;
+  }
+
+  // onNewGlobalObject is infallible, and thus is only allowed to return
+  // undefined as a resumption value. If it returns anything else, we throw.
+  // And if that happens, or if the hook itself throws, we invoke the
+  // uncaughtExceptionHook so that we never leave an exception pending on the
+  // cx. This allows JS_NewGlobalObject to avoid handling failures from
+  // debugger hooks.
+  RootedValue rv(cx);
+  RootedValue fval(cx, ObjectValue(*hook));
+  bool ok = js::Call(cx, fval, object, wrappedGlobal, &rv);
+  if (ok && !rv.isUndefined()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_RESUMPTION_VALUE_DISALLOWED);
+    ok = false;
+  }
+
+  return ok || handleUncaughtException(cx);
+}
+
+void DebugAPI::slowPathOnNewGlobalObject(JSContext* cx,
+                                         Handle<GlobalObject*> global) {
+  MOZ_ASSERT(!cx->runtime()->onNewGlobalObjectWatchers().isEmpty());
+  if (global->realm()->creationOptions().invisibleToDebugger()) {
+    return;
+  }
+
+  // Make a copy of the runtime's onNewGlobalObjectWatchers before running the
+  // handlers. Since one Debugger's handler can disable another's, the list
+  // can be mutated while we're walking it.
+  RootedObjectVector watchers(cx);
+  for (auto& dbg : cx->runtime()->onNewGlobalObjectWatchers()) {
+    MOZ_ASSERT(dbg.observesNewGlobalObject());
+    JSObject* obj = dbg.object;
+    JS::ExposeObjectToActiveJS(obj);
+    if (!watchers.append(obj)) {
+      if (cx->isExceptionPending()) {
+        cx->clearPendingException();
+      }
+      return;
+    }
+  }
+
+  // Preserve the debuggee's microtask event queue while we run the hooks, so
+  // the debugger's microtask checkpoints don't run from the debuggee's
+  // microtasks, and vice versa.
+  JS::AutoDebuggerJobQueueInterruption adjqi;
+  if (!adjqi.init(cx)) {
+    cx->clearPendingException();
+    return;
+  }
+
+  for (size_t i = 0; i < watchers.length(); i++) {
+    Debugger* dbg = Debugger::fromJSObject(watchers[i]);
+    EnterDebuggeeNoExecute nx(cx, *dbg, adjqi);
+
+    if (dbg->observesNewGlobalObject()) {
+      bool result = dbg->enterDebuggerHook(
+          cx, [&]() -> bool { return dbg->fireNewGlobalObject(cx, global); });
+      adjqi.runJobs();
+
+      if (!result) {
+        // Like other quiet hooks using dispatchQuietHook, this hook
+        // silently ignores all errors that propagate out of it and aren't
+        // already handled by the hook error reporting.
+        cx->clearPendingException();
+        break;
+      }
+    }
+  }
+  MOZ_ASSERT(!cx->isExceptionPending());
+}
+
+/* static */
+void DebugAPI::slowPathNotifyParticipatesInGC(uint64_t majorGCNumber,
+                                              Realm::DebuggerVector& dbgs) {
+  for (Realm::DebuggerVector::Range r = dbgs.all(); !r.empty(); r.popFront()) {
+    if (!r.front().dbg.unbarrieredGet()->debuggeeIsBeingCollected(
+            majorGCNumber)) {
+#ifdef DEBUG
+      fprintf(stderr,
+              "OOM while notifying observing Debuggers of a GC: The "
+              "onGarbageCollection\n"
+              "hook will not be fired for this GC for some Debuggers!\n");
+#endif
+      return;
+    }
+  }
+}
+
+/* static */
+Maybe<double> DebugAPI::allocationSamplingProbability(GlobalObject* global) {
+  Realm::DebuggerVector& dbgs = global->getDebuggers();
+  if (dbgs.empty()) {
+    return Nothing();
+  }
+
+  DebugOnly<Realm::DebuggerVectorEntry*> begin = dbgs.begin();
+
+  double probability = 0;
+  bool foundAnyDebuggers = false;
+  for (auto p = dbgs.begin(); p < dbgs.end(); p++) {
+    // The set of debuggers had better not change while we're iterating,
+    // such that the vector gets reallocated.
+    MOZ_ASSERT(dbgs.begin() == begin);
+    // Use unbarrieredGet() to prevent triggering read barrier while collecting,
+    // this is safe as long as dbgp does not escape.
+    Debugger* dbgp = p->dbg.unbarrieredGet();
+
+    if (dbgp->trackingAllocationSites) {
+      foundAnyDebuggers = true;
+      probability = std::max(dbgp->allocationSamplingProbability, probability);
+    }
+  }
+
+  return foundAnyDebuggers ? Some(probability) : Nothing();
+}
+
+/* static */
+bool DebugAPI::slowPathOnLogAllocationSite(JSContext* cx, HandleObject obj,
+                                           HandleSavedFrame frame,
+                                           mozilla::TimeStamp when,
+                                           Realm::DebuggerVector& dbgs) {
+  MOZ_ASSERT(!dbgs.empty());
+  mozilla::DebugOnly<Realm::DebuggerVectorEntry*> begin = dbgs.begin();
+
+  // Root all the Debuggers while we're iterating over them;
+  // appendAllocationSite calls Compartment::wrap, and thus can GC.
+  //
+  // SpiderMonkey protocol is generally for the caller to prove that it has
+  // rooted the stuff it's asking you to operate on (i.e. by passing a
+  // Handle), but in this case, we're iterating over a global's list of
+  // Debuggers, and globals only hold their Debuggers weakly.
+  Rooted<GCVector<JSObject*>> activeDebuggers(cx, GCVector<JSObject*>(cx));
+  for (auto p = dbgs.begin(); p < dbgs.end(); p++) {
+    if (!activeDebuggers.append(p->dbg->object)) {
+      return false;
+    }
+  }
+
+  for (auto p = dbgs.begin(); p < dbgs.end(); p++) {
+    // The set of debuggers had better not change while we're iterating,
+    // such that the vector gets reallocated.
+    MOZ_ASSERT(dbgs.begin() == begin);
+
+    if (p->dbg->trackingAllocationSites &&
+        !p->dbg->appendAllocationSite(cx, obj, frame, when)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+bool Debugger::isDebuggeeUnbarriered(const Realm* realm) const {
+  MOZ_ASSERT(realm);
+  return realm->isDebuggee() &&
+         debuggees.has(realm->unsafeUnbarrieredMaybeGlobal());
+}
+
+bool Debugger::appendAllocationSite(JSContext* cx, HandleObject obj,
+                                    HandleSavedFrame frame,
+                                    mozilla::TimeStamp when) {
+  MOZ_ASSERT(trackingAllocationSites);
+
+  AutoRealm ar(cx, object);
+  RootedObject wrappedFrame(cx, frame);
+  if (!cx->compartment()->wrap(cx, &wrappedFrame)) {
+    return false;
+  }
+
+  auto className = obj->getClass()->name;
+  auto size =
+      JS::ubi::Node(obj.get()).size(cx->runtime()->debuggerMallocSizeOf);
+  auto inNursery = gc::IsInsideNursery(obj);
+
+  if (!allocationsLog.emplaceBack(wrappedFrame, when, className, size,
+                                  inNursery)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+
+  if (allocationsLog.length() > maxAllocationsLogLength) {
+    allocationsLog.popFront();
+    MOZ_ASSERT(allocationsLog.length() == maxAllocationsLogLength);
+    allocationsLogOverflowed = true;
+  }
+
+  return true;
+}
+
+bool Debugger::firePromiseHook(JSContext* cx, Hook hook, HandleObject promise) {
+  MOZ_ASSERT(hook == OnNewPromise || hook == OnPromiseSettled);
+
+  RootedObject hookObj(cx, getHook(hook));
+  MOZ_ASSERT(hookObj);
+  MOZ_ASSERT(hookObj->isCallable());
+
+  RootedValue dbgObj(cx, ObjectValue(*promise));
+  if (!wrapDebuggeeValue(cx, &dbgObj)) {
+    return false;
+  }
+
+  // Like onNewGlobalObject, the Promise hooks are infallible and the comments
+  // in |Debugger::fireNewGlobalObject| apply here as well.
+  RootedValue fval(cx, ObjectValue(*hookObj));
+  RootedValue rv(cx);
+  bool ok = js::Call(cx, fval, object, dbgObj, &rv);
+  if (ok && !rv.isUndefined()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_RESUMPTION_VALUE_DISALLOWED);
+    ok = false;
+  }
+
+  return ok || handleUncaughtException(cx);
+}
+
+/* static */
+void Debugger::slowPathPromiseHook(JSContext* cx, Hook hook,
+                                   Handle<PromiseObject*> promise) {
+  MOZ_ASSERT(hook == OnNewPromise || hook == OnPromiseSettled);
+
+  if (hook == OnPromiseSettled) {
+    // We should be in the right compartment, but for simplicity always enter
+    // the promise's realm below.
+    cx->check(promise);
+  }
+
+  AutoRealm ar(cx, promise);
+
+  Debugger::dispatchQuietHook(
+      cx, [hook](Debugger* dbg) -> bool { return dbg->getHook(hook); },
+      [&](Debugger* dbg) -> bool {
+        return dbg->firePromiseHook(cx, hook, promise);
+      });
+}
+
+/* static */
+void DebugAPI::slowPathOnNewPromise(JSContext* cx,
+                                    Handle<PromiseObject*> promise) {
+  Debugger::slowPathPromiseHook(cx, Debugger::OnNewPromise, promise);
+}
+
+/* static */
+void DebugAPI::slowPathOnPromiseSettled(JSContext* cx,
+                                        Handle<PromiseObject*> promise) {
+  Debugger::slowPathPromiseHook(cx, Debugger::OnPromiseSettled, promise);
+}
+
+/*** Debugger code invalidation for observing execution *********************/
+
+class MOZ_RAII ExecutionObservableRealms
+    : public DebugAPI::ExecutionObservableSet {
+  HashSet<Realm*> realms_;
+  HashSet<Zone*> zones_;
+
+ public:
+  explicit ExecutionObservableRealms(JSContext* cx) : realms_(cx), zones_(cx) {}
+
+  bool add(Realm* realm) {
+    return realms_.put(realm) && zones_.put(realm->zone());
+  }
+
+  using RealmRange = HashSet<Realm*>::Range;
+  const HashSet<Realm*>* realms() const { return &realms_; }
+
+  const HashSet<Zone*>* zones() const override { return &zones_; }
+  bool shouldRecompileOrInvalidate(JSScript* script) const override {
+    return script->hasBaselineScript() && realms_.has(script->realm());
+  }
+  bool shouldMarkAsDebuggee(FrameIter& iter) const override {
+    // AbstractFramePtr can't refer to non-remateralized Ion frames or
+    // non-debuggee wasm frames, so if iter refers to one such, we know we
+    // don't match.
+    return iter.hasUsableAbstractFramePtr() && realms_.has(iter.realm());
+  }
+};
+
+// Given a particular AbstractFramePtr F that has become observable, this
+// represents the stack frames that need to be bailed out or marked as
+// debuggees, and the scripts that need to be recompiled, taking inlining into
+// account.
+class MOZ_RAII ExecutionObservableFrame
+    : public DebugAPI::ExecutionObservableSet {
+  AbstractFramePtr frame_;
+
+ public:
+  explicit ExecutionObservableFrame(AbstractFramePtr frame) : frame_(frame) {}
+
+  Zone* singleZone() const override {
+    // We never inline across realms, let alone across zones, so
+    // frames_'s script's zone is the only one of interest.
+    return frame_.script()->zone();
+  }
+
+  JSScript* singleScriptForZoneInvalidation() const override {
+    MOZ_CRASH(
+        "ExecutionObservableFrame shouldn't need zone-wide invalidation.");
+    return nullptr;
+  }
+
+  bool shouldRecompileOrInvalidate(JSScript* script) const override {
+    // Normally, *this represents exactly one script: the one frame_ is
+    // running.
+    //
+    // However, debug-mode OSR uses *this for both invalidating Ion frames,
+    // and recompiling the Baseline scripts that those Ion frames will bail
+    // out into. Suppose frame_ is an inline frame, executing a copy of its
+    // JSScript, S_inner, that has been inlined into the IonScript of some
+    // other JSScript, S_outer. We must match S_outer, to decide which Ion
+    // frame to invalidate; and we must match S_inner, to decide which
+    // Baseline script to recompile.
+    //
+    // Note that this does not, by design, invalidate *all* inliners of
+    // frame_.script(), as only frame_ is made observable, not
+    // frame_.script().
+    if (!script->hasBaselineScript()) {
+      return false;
+    }
+
+    if (frame_.hasScript() && script == frame_.script()) {
+      return true;
+    }
+
+    return frame_.isRematerializedFrame() &&
+           script == frame_.asRematerializedFrame()->outerScript();
+  }
+
+  bool shouldMarkAsDebuggee(FrameIter& iter) const override {
+    // AbstractFramePtr can't refer to non-remateralized Ion frames or
+    // non-debuggee wasm frames, so if iter refers to one such, we know we
+    // don't match.
+    //
+    // We never use this 'has' overload for frame invalidation, only for
+    // frame debuggee marking; so this overload doesn't need a parallel to
+    // the just-so inlining logic above.
+    return iter.hasUsableAbstractFramePtr() &&
+           iter.abstractFramePtr() == frame_;
+  }
+};
+
+class MOZ_RAII ExecutionObservableScript
+    : public DebugAPI::ExecutionObservableSet {
+  RootedScript script_;
+
+ public:
+  ExecutionObservableScript(JSContext* cx, JSScript* script)
+      : script_(cx, script) {}
+
+  Zone* singleZone() const override { return script_->zone(); }
+  JSScript* singleScriptForZoneInvalidation() const override { return script_; }
+  bool shouldRecompileOrInvalidate(JSScript* script) const override {
+    return script->hasBaselineScript() && script == script_;
+  }
+  bool shouldMarkAsDebuggee(FrameIter& iter) const override {
+    // AbstractFramePtr can't refer to non-remateralized Ion frames, and
+    // while a non-rematerialized Ion frame may indeed be running script_,
+    // we cannot mark them as debuggees until they bail out.
+    //
+    // Upon bailing out, any newly constructed Baseline frames that came
+    // from Ion frames with scripts that are isDebuggee() is marked as
+    // debuggee. This is correct in that the only other way a frame may be
+    // marked as debuggee is via Debugger.Frame reflection, which would
+    // have rematerialized any Ion frames.
+    //
+    // Also AbstractFramePtr can't refer to non-debuggee wasm frames, so if
+    // iter refers to one such, we know we don't match.
+    return iter.hasUsableAbstractFramePtr() && !iter.isWasm() &&
+           iter.abstractFramePtr().script() == script_;
+  }
+};
+
+/* static */
+bool Debugger::updateExecutionObservabilityOfFrames(
+    JSContext* cx, const DebugAPI::ExecutionObservableSet& obs,
+    IsObserving observing) {
+  AutoSuppressProfilerSampling suppressProfilerSampling(cx);
+
+  {
+    jit::JitContext jctx(cx, nullptr);
+    if (!jit::RecompileOnStackBaselineScriptsForDebugMode(cx, obs, observing)) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+
+  AbstractFramePtr oldestEnabledFrame;
+  for (AllFramesIter iter(cx); !iter.done(); ++iter) {
+    if (obs.shouldMarkAsDebuggee(iter)) {
+      if (observing) {
+        if (!iter.abstractFramePtr().isDebuggee()) {
+          oldestEnabledFrame = iter.abstractFramePtr();
+          oldestEnabledFrame.setIsDebuggee();
+        }
+        if (iter.abstractFramePtr().isWasmDebugFrame()) {
+          iter.abstractFramePtr().asWasmDebugFrame()->observe(cx);
+        }
+      } else {
+#ifdef DEBUG
+        // Debugger.Frame lifetimes are managed by the debug epilogue,
+        // so in general it's unsafe to unmark a frame if it has a
+        // Debugger.Frame associated with it.
+        MOZ_ASSERT(!DebugAPI::inFrameMaps(iter.abstractFramePtr()));
+#endif
+        iter.abstractFramePtr().unsetIsDebuggee();
+      }
+    }
+  }
+
+  // See comment in unsetPrevUpToDateUntil.
+  if (oldestEnabledFrame) {
+    AutoRealm ar(cx, oldestEnabledFrame.environmentChain());
+    DebugEnvironments::unsetPrevUpToDateUntil(cx, oldestEnabledFrame);
+  }
+
+  return true;
+}
+
+static inline void MarkJitScriptActiveIfObservable(
+    JSScript* script, const DebugAPI::ExecutionObservableSet& obs) {
+  if (obs.shouldRecompileOrInvalidate(script)) {
+    script->jitScript()->setActive();
+  }
+}
+
+static bool AppendAndInvalidateScript(JSContext* cx, Zone* zone,
+                                      JSScript* script,
+                                      jit::RecompileInfoVector& invalid,
+                                      Vector<JSScript*>& scripts) {
+  // Enter the script's realm as AddPendingInvalidation attempts to
+  // cancel off-thread compilations, whose books are kept on the
+  // script's realm.
+  MOZ_ASSERT(script->zone() == zone);
+  AutoRealm ar(cx, script);
+  AddPendingInvalidation(invalid, script);
+  return scripts.append(script);
+}
+
+static bool UpdateExecutionObservabilityOfScriptsInZone(
+    JSContext* cx, Zone* zone, const DebugAPI::ExecutionObservableSet& obs,
+    Debugger::IsObserving observing) {
+  using namespace js::jit;
+
+  AutoSuppressProfilerSampling suppressProfilerSampling(cx);
+
+  JSFreeOp* fop = cx->runtime()->defaultFreeOp();
+
+  Vector<JSScript*> scripts(cx);
+
+  // Iterate through observable scripts, invalidating their Ion scripts and
+  // appending them to a vector for discarding their baseline scripts later.
+  {
+    RecompileInfoVector invalid;
+    if (JSScript* script = obs.singleScriptForZoneInvalidation()) {
+      if (obs.shouldRecompileOrInvalidate(script)) {
+        if (!AppendAndInvalidateScript(cx, zone, script, invalid, scripts)) {
+          return false;
+        }
+      }
+    } else {
+      for (auto base = zone->cellIter<BaseScript>(); !base.done();
+           base.next()) {
+        if (!base->hasJitScript()) {
+          continue;
+        }
+        JSScript* script = base->asJSScript();
+        if (obs.shouldRecompileOrInvalidate(script)) {
+          if (!AppendAndInvalidateScript(cx, zone, script, invalid, scripts)) {
+            return false;
+          }
+        }
+      }
+    }
+    Invalidate(cx, invalid);
+  }
+
+  // Code below this point must be infallible to ensure the active bit of
+  // BaselineScripts is in a consistent state.
+  //
+  // Mark active baseline scripts in the observable set so that they don't
+  // get discarded. They will be recompiled.
+  for (JitActivationIterator actIter(cx); !actIter.done(); ++actIter) {
+    if (actIter->compartment()->zone() != zone) {
+      continue;
+    }
+
+    for (OnlyJSJitFrameIter iter(actIter); !iter.done(); ++iter) {
+      const JSJitFrameIter& frame = iter.frame();
+      switch (frame.type()) {
+        case FrameType::BaselineJS:
+          MarkJitScriptActiveIfObservable(frame.script(), obs);
+          break;
+        case FrameType::IonJS:
+          MarkJitScriptActiveIfObservable(frame.script(), obs);
+          for (InlineFrameIterator inlineIter(cx, &frame); inlineIter.more();
+               ++inlineIter) {
+            MarkJitScriptActiveIfObservable(inlineIter.script(), obs);
+          }
+          break;
+        default:;
+      }
+    }
+  }
+
+  // Iterate through the scripts again and finish discarding
+  // BaselineScripts. This must be done as a separate phase as we can only
+  // discard the BaselineScript on scripts that have no IonScript.
+  for (size_t i = 0; i < scripts.length(); i++) {
+    MOZ_ASSERT_IF(scripts[i]->isDebuggee(), observing);
+    if (!scripts[i]->jitScript()->active()) {
+      FinishDiscardBaselineScript(fop, scripts[i]);
+    }
+    scripts[i]->jitScript()->resetActive();
+  }
+
+  // Iterate through all wasm instances to find ones that need to be updated.
+  for (RealmsInZoneIter r(zone); !r.done(); r.next()) {
+    for (wasm::Instance* instance : r->wasm.instances()) {
+      if (!instance->debugEnabled()) {
+        continue;
+      }
+
+      bool enableTrap = observing == Debugger::Observing;
+      instance->debug().ensureEnterFrameTrapsState(cx, enableTrap);
+    }
+  }
+
+  return true;
+}
+
+/* static */
+bool Debugger::updateExecutionObservabilityOfScripts(
+    JSContext* cx, const DebugAPI::ExecutionObservableSet& obs,
+    IsObserving observing) {
+  if (Zone* zone = obs.singleZone()) {
+    return UpdateExecutionObservabilityOfScriptsInZone(cx, zone, obs,
+                                                       observing);
+  }
+
+  using ZoneRange = DebugAPI::ExecutionObservableSet::ZoneRange;
+  for (ZoneRange r = obs.zones()->all(); !r.empty(); r.popFront()) {
+    if (!UpdateExecutionObservabilityOfScriptsInZone(cx, r.front(), obs,
+                                                     observing)) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+template <typename FrameFn>
+/* static */
+void Debugger::forEachOnStackDebuggerFrame(AbstractFramePtr frame, FrameFn fn) {
+  for (Realm::DebuggerVectorEntry& entry : frame.global()->getDebuggers()) {
+    Debugger* dbg = entry.dbg;
+    if (FrameMap::Ptr frameEntry = dbg->frames.lookup(frame)) {
+      fn(dbg, frameEntry->value());
+    }
+  }
+}
+
+template <typename FrameFn>
+/* static */
+void Debugger::forEachOnStackOrSuspendedDebuggerFrame(JSContext* cx,
+                                                      AbstractFramePtr frame,
+                                                      FrameFn fn) {
+  Rooted<AbstractGeneratorObject*> genObj(
+      cx, frame.isGeneratorFrame() ? GetGeneratorObjectForFrame(cx, frame)
+                                   : nullptr);
+
+  for (Realm::DebuggerVectorEntry& entry : frame.global()->getDebuggers()) {
+    Debugger* dbg = entry.dbg;
+
+    DebuggerFrame* frameObj = nullptr;
+    if (FrameMap::Ptr frameEntry = dbg->frames.lookup(frame)) {
+      frameObj = frameEntry->value();
+    } else if (GeneratorWeakMap::Ptr frameEntry =
+                   dbg->generatorFrames.lookup(genObj)) {
+      frameObj = frameEntry->value();
+    }
+
+    if (frameObj) {
+      fn(dbg, frameObj);
+    }
+  }
+}
+
+/* static */
+bool Debugger::getDebuggerFrames(AbstractFramePtr frame,
+                                 MutableHandle<DebuggerFrameVector> frames) {
+  bool hadOOM = false;
+  forEachOnStackDebuggerFrame(frame, [&](Debugger*, DebuggerFrame* frameobj) {
+    if (!hadOOM && !frames.append(frameobj)) {
+      hadOOM = true;
+    }
+  });
+  return !hadOOM;
+}
+
+/* static */
+bool Debugger::updateExecutionObservability(
+    JSContext* cx, DebugAPI::ExecutionObservableSet& obs,
+    IsObserving observing) {
+  if (!obs.singleZone() && obs.zones()->empty()) {
+    return true;
+  }
+
+  // Invalidate scripts first so we can set the needsArgsObj flag on scripts
+  // before patching frames.
+  return updateExecutionObservabilityOfScripts(cx, obs, observing) &&
+         updateExecutionObservabilityOfFrames(cx, obs, observing);
+}
+
+/* static */
+bool Debugger::ensureExecutionObservabilityOfScript(JSContext* cx,
+                                                    JSScript* script) {
+  if (script->isDebuggee()) {
+    return true;
+  }
+  ExecutionObservableScript obs(cx, script);
+  return updateExecutionObservability(cx, obs, Observing);
+}
+
+/* static */
+bool DebugAPI::ensureExecutionObservabilityOfOsrFrame(
+    JSContext* cx, AbstractFramePtr osrSourceFrame) {
+  MOZ_ASSERT(osrSourceFrame.isDebuggee());
+  if (osrSourceFrame.script()->hasBaselineScript() &&
+      osrSourceFrame.script()->baselineScript()->hasDebugInstrumentation()) {
+    return true;
+  }
+  ExecutionObservableFrame obs(osrSourceFrame);
+  return Debugger::updateExecutionObservabilityOfFrames(cx, obs, Observing);
+}
+
+/* static */
+bool Debugger::ensureExecutionObservabilityOfFrame(JSContext* cx,
+                                                   AbstractFramePtr frame) {
+  MOZ_ASSERT_IF(frame.hasScript() && frame.script()->isDebuggee(),
+                frame.isDebuggee());
+  MOZ_ASSERT_IF(frame.isWasmDebugFrame(), frame.wasmInstance()->debugEnabled());
+  if (frame.isDebuggee()) {
+    return true;
+  }
+  ExecutionObservableFrame obs(frame);
+  return updateExecutionObservabilityOfFrames(cx, obs, Observing);
+}
+
+/* static */
+bool Debugger::ensureExecutionObservabilityOfRealm(JSContext* cx,
+                                                   Realm* realm) {
+  if (realm->debuggerObservesAllExecution()) {
+    return true;
+  }
+  ExecutionObservableRealms obs(cx);
+  if (!obs.add(realm)) {
+    return false;
+  }
+  realm->updateDebuggerObservesAllExecution();
+  return updateExecutionObservability(cx, obs, Observing);
+}
+
+/* static */
+bool Debugger::hookObservesAllExecution(Hook which) {
+  return which == OnEnterFrame;
+}
+
+Debugger::IsObserving Debugger::observesAllExecution() const {
+  if (!!getHook(OnEnterFrame)) {
+    return Observing;
+  }
+  return NotObserving;
+}
+
+Debugger::IsObserving Debugger::observesAsmJS() const {
+  if (!allowUnobservedAsmJS) {
+    return Observing;
+  }
+  return NotObserving;
+}
+
+Debugger::IsObserving Debugger::observesCoverage() const {
+  if (collectCoverageInfo) {
+    return Observing;
+  }
+  return NotObserving;
+}
+
+Debugger::IsObserving Debugger::observesNativeCalls() const {
+  if (getHook(Debugger::OnNativeCall)) {
+    return Observing;
+  }
+  return NotObserving;
+}
+
+// Toggle whether this Debugger's debuggees observe all execution. This is
+// called when a hook that observes all execution is set or unset. See
+// hookObservesAllExecution.
+bool Debugger::updateObservesAllExecutionOnDebuggees(JSContext* cx,
+                                                     IsObserving observing) {
+  ExecutionObservableRealms obs(cx);
+
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    GlobalObject* global = r.front();
+    JS::Realm* realm = global->realm();
+
+    if (realm->debuggerObservesAllExecution() == observing) {
+      continue;
+    }
+
+    // It's expensive to eagerly invalidate and recompile a realm,
+    // so add the realm to the set only if we are observing.
+    if (observing && !obs.add(realm)) {
+      return false;
+    }
+  }
+
+  if (!updateExecutionObservability(cx, obs, observing)) {
+    return false;
+  }
+
+  using RealmRange = ExecutionObservableRealms::RealmRange;
+  for (RealmRange r = obs.realms()->all(); !r.empty(); r.popFront()) {
+    r.front()->updateDebuggerObservesAllExecution();
+  }
+
+  return true;
+}
+
+bool Debugger::updateObservesCoverageOnDebuggees(JSContext* cx,
+                                                 IsObserving observing) {
+  ExecutionObservableRealms obs(cx);
+
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    GlobalObject* global = r.front();
+    Realm* realm = global->realm();
+
+    if (realm->debuggerObservesCoverage() == observing) {
+      continue;
+    }
+
+    // Invalidate and recompile a realm to add or remove PCCounts
+    // increments. We have to eagerly invalidate, as otherwise we might have
+    // dangling pointers to freed PCCounts.
+    if (!obs.add(realm)) {
+      return false;
+    }
+  }
+
+  // If any frame on the stack belongs to the debuggee, then we cannot update
+  // the ScriptCounts, because this would imply to invalidate a Debugger.Frame
+  // to recompile it with/without ScriptCount support.
+  for (FrameIter iter(cx); !iter.done(); ++iter) {
+    if (obs.shouldMarkAsDebuggee(iter)) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_NOT_IDLE);
+      return false;
+    }
+  }
+
+  if (!updateExecutionObservability(cx, obs, observing)) {
+    return false;
+  }
+
+  // All realms can safely be toggled, and all scripts will be recompiled.
+  // Thus we can update each realm accordingly.
+  using RealmRange = ExecutionObservableRealms::RealmRange;
+  for (RealmRange r = obs.realms()->all(); !r.empty(); r.popFront()) {
+    r.front()->updateDebuggerObservesCoverage();
+  }
+
+  return true;
+}
+
+void Debugger::updateObservesAsmJSOnDebuggees(IsObserving observing) {
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    GlobalObject* global = r.front();
+    Realm* realm = global->realm();
+
+    if (realm->debuggerObservesAsmJS() == observing) {
+      continue;
+    }
+
+    realm->updateDebuggerObservesAsmJS();
+  }
+}
+
+/*** Allocations Tracking ***************************************************/
+
+/* static */
+bool Debugger::cannotTrackAllocations(const GlobalObject& global) {
+  auto existingCallback = global.realm()->getAllocationMetadataBuilder();
+  return existingCallback && existingCallback != &SavedStacks::metadataBuilder;
+}
+
+/* static */
+bool DebugAPI::isObservedByDebuggerTrackingAllocations(
+    const GlobalObject& debuggee) {
+  for (Realm::DebuggerVectorEntry& entry : debuggee.getDebuggers()) {
+    // Use unbarrieredGet() to prevent triggering read barrier while
+    // collecting, this is safe as long as dbg does not escape.
+    Debugger* dbg = entry.dbg.unbarrieredGet();
+    if (dbg->trackingAllocationSites) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+/* static */
+bool Debugger::addAllocationsTracking(JSContext* cx,
+                                      Handle<GlobalObject*> debuggee) {
+  // Precondition: the given global object is being observed by at least one
+  // Debugger that is tracking allocations.
+  MOZ_ASSERT(DebugAPI::isObservedByDebuggerTrackingAllocations(*debuggee));
+
+  if (Debugger::cannotTrackAllocations(*debuggee)) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_OBJECT_METADATA_CALLBACK_ALREADY_SET);
+    return false;
+  }
+
+  debuggee->realm()->setAllocationMetadataBuilder(
+      &SavedStacks::metadataBuilder);
+  debuggee->realm()->chooseAllocationSamplingProbability();
+  return true;
+}
+
+/* static */
+void Debugger::removeAllocationsTracking(GlobalObject& global) {
+  // If there are still Debuggers that are observing allocations, we cannot
+  // remove the metadata callback yet. Recompute the sampling probability
+  // based on the remaining debuggers' needs.
+  if (DebugAPI::isObservedByDebuggerTrackingAllocations(global)) {
+    global.realm()->chooseAllocationSamplingProbability();
+    return;
+  }
+
+  if (!global.realm()->runtimeFromMainThread()->recordAllocationCallback) {
+    // Something like the Gecko Profiler could request from the the JS runtime
+    // to record allocations. If it is recording allocations, then do not
+    // destroy the allocation metadata builder at this time.
+    global.realm()->forgetAllocationMetadataBuilder();
+  }
+}
+
+bool Debugger::addAllocationsTrackingForAllDebuggees(JSContext* cx) {
+  MOZ_ASSERT(trackingAllocationSites);
+
+  // We don't want to end up in a state where we added allocations
+  // tracking to some of our debuggees, but failed to do so for
+  // others. Before attempting to start tracking allocations in *any* of
+  // our debuggees, ensure that we will be able to track allocations for
+  // *all* of our debuggees.
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    if (Debugger::cannotTrackAllocations(*r.front().get())) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_OBJECT_METADATA_CALLBACK_ALREADY_SET);
+      return false;
+    }
+  }
+
+  Rooted<GlobalObject*> g(cx);
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    // This should always succeed, since we already checked for the
+    // error case above.
+    g = r.front().get();
+    MOZ_ALWAYS_TRUE(Debugger::addAllocationsTracking(cx, g));
+  }
+
+  return true;
+}
+
+void Debugger::removeAllocationsTrackingForAllDebuggees() {
+  for (WeakGlobalObjectSet::Range r = debuggees.all(); !r.empty();
+       r.popFront()) {
+    Debugger::removeAllocationsTracking(*r.front().get());
+  }
+
+  allocationsLog.clear();
+}
+
+/*** Debugger JSObjects *****************************************************/
+
+template <typename F>
+inline void Debugger::forEachWeakMap(const F& f) {
+  f(generatorFrames);
+  f(objects);
+  f(environments);
+  f(scripts);
+  f(sources);
+  f(wasmInstanceScripts);
+  f(wasmInstanceSources);
+}
+
+void Debugger::traceCrossCompartmentEdges(JSTracer* trc) {
+  forEachWeakMap(
+      [trc](auto& weakMap) { weakMap.traceCrossCompartmentEdges(trc); });
+}
+
+/*
+ * Ordinarily, WeakMap keys and values are marked because at some point it was
+ * discovered that the WeakMap was live; that is, some object containing the
+ * WeakMap was marked during mark phase.
+ *
+ * However, during zone GC, we have to do something about cross-compartment
+ * edges in non-GC'd compartments. Since the source may be live, we
+ * conservatively assume it is and mark the edge.
+ *
+ * Each Debugger object keeps five cross-compartment WeakMaps: objects, scripts,
+ * lazy scripts, script source objects, and environments. They have the property
+ * that all their values are in the same compartment as the Debugger object,
+ * but we have to mark the keys and the private pointer in the wrapper object.
+ *
+ * We must scan all Debugger objects regardless of whether they *currently* have
+ * any debuggees in a compartment being GC'd, because the WeakMap entries
+ * persist even when debuggees are removed.
+ *
+ * This happens during the initial mark phase, not iterative marking, because
+ * all the edges being reported here are strong references.
+ *
+ * This method is also used during compacting GC to update cross compartment
+ * pointers into zones that are being compacted.
+ */
+/* static */
+void DebugAPI::traceCrossCompartmentEdges(JSTracer* trc) {
+  MOZ_ASSERT(JS::RuntimeHeapIsMajorCollecting());
+
+  JSRuntime* rt = trc->runtime();
+  gc::State state = rt->gc.state();
+
+  for (Debugger* dbg : rt->debuggerList()) {
+    Zone* zone = MaybeForwarded(dbg->object.get())->zone();
+    if (!zone->isCollecting() || state == gc::State::Compact) {
+      dbg->traceCrossCompartmentEdges(trc);
+    }
+  }
+}
+
+#ifdef DEBUG
+
+static bool RuntimeHasDebugger(JSRuntime* rt, Debugger* dbg) {
+  for (Debugger* d : rt->debuggerList()) {
+    if (d == dbg) {
+      return true;
+    }
+  }
+  return false;
+}
+
+/* static */
+bool DebugAPI::edgeIsInDebuggerWeakmap(JSRuntime* rt, JSObject* src,
+                                       JS::GCCellPtr dst) {
+  if (!Debugger::isChildJSObject(src)) {
+    return false;
+  }
+
+  if (src->is<DebuggerFrame>()) {
+    DebuggerFrame* frame = &src->as<DebuggerFrame>();
+    Debugger* dbg = frame->owner();
+    MOZ_ASSERT(RuntimeHasDebugger(rt, dbg));
+
+    if (dst.is<BaseScript>()) {
+      // The generatorFrames map is not keyed on the associated JSScript. Get
+      // the key from the source object and check everything matches.
+      AbstractGeneratorObject* genObj = &frame->unwrappedGenerator();
+      return frame->generatorScript() == &dst.as<BaseScript>() &&
+             dbg->generatorFrames.hasEntry(genObj, src);
+    }
+    return dst.is<JSObject>() &&
+           dst.as<JSObject>().is<AbstractGeneratorObject>() &&
+           dbg->generatorFrames.hasEntry(
+               &dst.as<JSObject>().as<AbstractGeneratorObject>(), src);
+  }
+  if (src->is<DebuggerObject>()) {
+    Debugger* dbg = src->as<DebuggerObject>().owner();
+    MOZ_ASSERT(RuntimeHasDebugger(rt, dbg));
+    return dst.is<JSObject>() &&
+           dbg->objects.hasEntry(&dst.as<JSObject>(), src);
+  }
+  if (src->is<DebuggerEnvironment>()) {
+    Debugger* dbg = src->as<DebuggerEnvironment>().owner();
+    MOZ_ASSERT(RuntimeHasDebugger(rt, dbg));
+    return dst.is<JSObject>() &&
+           dbg->environments.hasEntry(&dst.as<JSObject>(), src);
+  }
+  if (src->is<DebuggerScript>()) {
+    Debugger* dbg = src->as<DebuggerScript>().owner();
+    MOZ_ASSERT(RuntimeHasDebugger(rt, dbg));
+
+    return src->as<DebuggerScript>().getReferent().match(
+        [=](BaseScript* script) {
+          return dst.is<BaseScript>() && script == &dst.as<BaseScript>() &&
+                 dbg->scripts.hasEntry(script, src);
+        },
+        [=](WasmInstanceObject* instance) {
+          return dst.is<JSObject>() && instance == &dst.as<JSObject>() &&
+                 dbg->wasmInstanceScripts.hasEntry(instance, src);
+        });
+  }
+  if (src->is<DebuggerSource>()) {
+    Debugger* dbg = src->as<DebuggerSource>().owner();
+    MOZ_ASSERT(RuntimeHasDebugger(rt, dbg));
+
+    return src->as<DebuggerSource>().getReferent().match(
+        [=](ScriptSourceObject* sso) {
+          return dst.is<JSObject>() && sso == &dst.as<JSObject>() &&
+                 dbg->sources.hasEntry(sso, src);
+        },
+        [=](WasmInstanceObject* instance) {
+          return dst.is<JSObject>() && instance == &dst.as<JSObject>() &&
+                 dbg->wasmInstanceSources.hasEntry(instance, src);
+        });
+  }
+  MOZ_ASSERT_UNREACHABLE("Unhandled cross-compartment edge");
+}
+
+#endif
+
+/* See comments in DebugAPI.h. */
+void DebugAPI::traceFramesWithLiveHooks(JSTracer* tracer) {
+  JSRuntime* rt = tracer->runtime();
+
+  // Note that we must loop over all Debuggers here, not just those known to be
+  // reachable from JavaScript. The existence of hooks set on a Debugger.Frame
+  // for a live stack frame makes the Debuger.Frame (and hence its Debugger)
+  // reachable.
+  for (Debugger* dbg : rt->debuggerList()) {
+    // Callback tracers set their own traversal boundaries, but otherwise we're
+    // only interested in Debugger.Frames participating in the collection.
+    if (!dbg->zone()->isGCMarking() && !tracer->isCallbackTracer()) {
+      continue;
+    }
+
+    for (Debugger::FrameMap::Range r = dbg->frames.all(); !r.empty();
+         r.popFront()) {
+      HeapPtr<DebuggerFrame*>& frameobj = r.front().value();
+      MOZ_ASSERT(frameobj->isOnStackMaybeForwarded());
+      if (frameobj->hasAnyHooks()) {
+        TraceEdge(tracer, &frameobj, "Debugger.Frame with live hooks");
+      }
+    }
+  }
+}
+
+void DebugAPI::slowPathTraceGeneratorFrame(JSTracer* tracer,
+                                           AbstractGeneratorObject* generator) {
+  MOZ_ASSERT(generator->realm()->isDebuggee());
+
+  // Ignore generic tracers.
+  //
+  // There are two kinds of generic tracers we need to bar: MovingTracers used
+  // by compacting GC; and CompartmentCheckTracers.
+  //
+  // MovingTracers are used by the compacting GC to update pointers to objects
+  // that have been moved: the MovingTracer checks each outgoing pointer to see
+  // if it refers to a forwarding pointer, and if so, updates the pointer stored
+  // in the object.
+  //
+  // Generator objects are background finalized, so the compacting GC assumes it
+  // can update their pointers in the background as well. Since we treat
+  // generator objects as having an owning edge to their Debugger.Frame objects,
+  // a helper thread trying to update a generator object will end up calling
+  // this function. However, it is verboten to do weak map lookups (e.g., in
+  // Debugger::generatorFrames) off the main thread, since MovableCellHasher
+  // must consult the Zone to find the key's unique id.
+  //
+  // Fortunately, it's not necessary for compacting GC to worry about that edge
+  // in the first place: the edge isn't a literal pointer stored on the
+  // generator object, it's only inferred from the realm's debuggee status and
+  // its Debuggers' generatorFrames weak maps. Those get relocated when the
+  // Debugger itself is visited, so compacting GC can just ignore this edge.
+  //
+  // CompartmentCheckTracers walk the graph and verify that all
+  // cross-compartment edges are recorded in the cross-compartment wrapper
+  // tables. But edges between Debugger.Foo objects and their referents are not
+  // in the CCW tables, so a CrossCompartmentCheckTracers also calls
+  // DebugAPI::edgeIsInDebuggerWeakmap to see if a given cross-compartment edge
+  // is accounted for there. However, edgeIsInDebuggerWeakmap only handles
+  // debugger -> debuggee edges, so it won't recognize the edge we're
+  // potentially traversing here, from a generator object to its Debugger.Frame.
+  //
+  // But since the purpose of this function is to retrieve such edges, if they
+  // exist, from the very tables that edgeIsInDebuggerWeakmap would consult,
+  // we're at no risk of reporting edges that they do not cover. So we can
+  // safely hide the edges from CompartmentCheckTracers.
+  //
+  // We can't quite recognize MovingTracers and CompartmentCheckTracers
+  // precisely, but they're both generic tracers, so we just show them all the
+  // door. This means the generator -> Debugger.Frame edge is going to be
+  // invisible to some traversals. We'll cope with that when it's a problem.
+  if (tracer->isGenericTracer()) {
+    return;
+  }
+
+  for (Realm::DebuggerVectorEntry& entry : generator->realm()->getDebuggers()) {
+    Debugger* dbg = entry.dbg.unbarrieredGet();
+
+    if (Debugger::GeneratorWeakMap::Ptr entry =
+            dbg->generatorFrames.lookupUnbarriered(generator)) {
+      HeapPtr<DebuggerFrame*>& frameObj = entry->value();
+      if (frameObj->hasAnyHooks()) {
+        // See comment above.
+        TraceCrossCompartmentEdge(tracer, generator, &frameObj,
+                                  "Debugger.Frame with hooks for generator");
+      }
+    }
+  }
+}
+
+/* static */
+void DebugAPI::traceAllForMovingGC(JSTracer* trc) {
+  JSRuntime* rt = trc->runtime();
+  for (Debugger* dbg : rt->debuggerList()) {
+    dbg->traceForMovingGC(trc);
+  }
+}
+
+/*
+ * Trace all debugger-owned GC things unconditionally. This is used during
+ * compacting GC and in minor GC: the minor GC cannot apply the weak constraints
+ * of the full GC because it visits only part of the heap.
+ */
+void Debugger::traceForMovingGC(JSTracer* trc) {
+  trace(trc);
+
+  for (WeakGlobalObjectSet::Enum e(debuggees); !e.empty(); e.popFront()) {
+    TraceEdge(trc, &e.mutableFront(), "Global Object");
+  }
+}
+
+/* static */
+void Debugger::traceObject(JSTracer* trc, JSObject* obj) {
+  if (Debugger* dbg = Debugger::fromJSObject(obj)) {
+    dbg->trace(trc);
+  }
+}
+
+void Debugger::trace(JSTracer* trc) {
+  TraceEdge(trc, &object, "Debugger Object");
+
+  TraceNullableEdge(trc, &uncaughtExceptionHook, "hooks");
+
+  // Mark Debugger.Frame objects. Since the Debugger is reachable, JS could call
+  // getNewestFrame and then walk the stack, so these are all reachable from JS.
+  //
+  // Note that if a Debugger.Frame has hooks set, it must be retained even if
+  // its Debugger is unreachable, since JS could observe that its hooks did not
+  // fire. That case is handled by DebugAPI::traceFrames.
+  //
+  // (We have weakly-referenced Debugger.Frame objects as well, for suspended
+  // generator frames; these are traced via generatorFrames just below.)
+  for (FrameMap::Range r = frames.all(); !r.empty(); r.popFront()) {
+    HeapPtr<DebuggerFrame*>& frameobj = r.front().value();
+    TraceEdge(trc, &frameobj, "live Debugger.Frame");
+    MOZ_ASSERT(frameobj->isOnStackMaybeForwarded());
+  }
+
+  allocationsLog.trace(trc);
+
+  forEachWeakMap([trc](auto& weakMap) { weakMap.trace(trc); });
+}
+
+/* static */
+void DebugAPI::traceFromRealm(JSTracer* trc, Realm* realm) {
+  for (Realm::DebuggerVectorEntry& entry : realm->getDebuggers()) {
+    TraceEdge(trc, &entry.debuggerLink, "realm debugger");
+  }
+}
+
+/* static */
+void DebugAPI::sweepAll(JSFreeOp* fop) {
+  JSRuntime* rt = fop->runtime();
+
+  Debugger* next;
+  for (Debugger* dbg = rt->debuggerList().getFirst(); dbg; dbg = next) {
+    next = dbg->getNext();
+
+    // Debugger.Frames for generator calls bump the JSScript's
+    // generatorObserverCount, so the JIT will instrument the code to notify
+    // Debugger when the generator is resumed. When a Debugger.Frame gets GC'd,
+    // generatorObserverCount needs to be decremented. It's much easier to do
+    // this when we know that all parties involved - the Debugger.Frame, the
+    // generator object, and the JSScript - have not yet been finalized.
+    //
+    // Since DebugAPI::sweepAll is called after everything is marked, but before
+    // anything has been finalized, this is the perfect place to drop the count.
+    if (dbg->zone()->isGCSweeping()) {
+      for (Debugger::GeneratorWeakMap::Enum e(dbg->generatorFrames); !e.empty();
+           e.popFront()) {
+        DebuggerFrame* frameObj = e.front().value();
+        if (IsAboutToBeFinalizedUnbarriered(&frameObj)) {
+          // If the DebuggerFrame is being finalized, that means either:
+          //  1) It is not present in "frames".
+          //  2) The Debugger itself is also being finalized.
+          //
+          // In the first case, passing the frame is not necessary because there
+          // isn't a frame entry to clear, and in the second case,
+          // removeDebuggeeGlobal below will iterate and remove the entries
+          // anyway, so things will be cleaned up properly.
+          Debugger::terminateDebuggerFrame(fop, dbg, frameObj, NullFramePtr(),
+                                           nullptr, &e);
+        }
+      }
+    }
+
+    // Detach dying debuggers and debuggees from each other. Since this
+    // requires access to both objects it must be done before either
+    // object is finalized.
+    bool debuggerDying = IsAboutToBeFinalized(&dbg->object);
+    for (WeakGlobalObjectSet::Enum e(dbg->debuggees); !e.empty();
+         e.popFront()) {
+      GlobalObject* global = e.front().unbarrieredGet();
+      if (debuggerDying || IsAboutToBeFinalizedUnbarriered(&global)) {
+        dbg->removeDebuggeeGlobal(fop, e.front().unbarrieredGet(), &e,
+                                  Debugger::FromSweep::Yes);
+      }
+    }
+
+    if (debuggerDying) {
+      fop->delete_(dbg->object, dbg, MemoryUse::Debugger);
+    }
+
+    dbg = next;
+  }
+}
+
+static inline bool SweepZonesInSameGroup(Zone* a, Zone* b) {
+  // Ensure two zones are swept in the same sweep group by adding an edge
+  // between them in each direction.
+  return a->addSweepGroupEdgeTo(b) && b->addSweepGroupEdgeTo(a);
+}
+
+/* static */
+bool DebugAPI::findSweepGroupEdges(JSRuntime* rt) {
+  // Ensure that debuggers and their debuggees are finalized in the same group
+  // by adding edges in both directions for debuggee zones. These are weak
+  // references that are not in the cross compartment wrapper map.
+
+  for (Debugger* dbg : rt->debuggerList()) {
+    Zone* debuggerZone = dbg->object->zone();
+    if (!debuggerZone->isGCMarking()) {
+      continue;
+    }
+
+    for (auto e = dbg->debuggeeZones.all(); !e.empty(); e.popFront()) {
+      Zone* debuggeeZone = e.front();
+      if (!debuggeeZone->isGCMarking()) {
+        continue;
+      }
+
+      if (!SweepZonesInSameGroup(debuggerZone, debuggeeZone)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+template <class UnbarrieredKey, class Wrapper, bool InvisibleKeysOk>
+bool DebuggerWeakMap<UnbarrieredKey, Wrapper,
+                     InvisibleKeysOk>::findSweepGroupEdges() {
+  Zone* debuggerZone = zone();
+  MOZ_ASSERT(debuggerZone->isGCMarking());
+  for (Enum e(*this); !e.empty(); e.popFront()) {
+    MOZ_ASSERT(e.front().value()->zone() == debuggerZone);
+
+    Zone* keyZone = e.front().key()->zone();
+    if (keyZone->isGCMarking() &&
+        !SweepZonesInSameGroup(debuggerZone, keyZone)) {
+      return false;
+    }
+  }
+
+  // Add in edges for delegates, if relevant for the key type.
+  return Base::findSweepGroupEdges();
+}
+
+const JSClassOps DebuggerInstanceObject::classOps_ = {
+    nullptr,                // addProperty
+    nullptr,                // delProperty
+    nullptr,                // enumerate
+    nullptr,                // newEnumerate
+    nullptr,                // resolve
+    nullptr,                // mayResolve
+    nullptr,                // finalize
+    nullptr,                // call
+    nullptr,                // hasInstance
+    nullptr,                // construct
+    Debugger::traceObject,  // trace
+};
+
+const JSClass DebuggerInstanceObject::class_ = {
+    "Debugger",
+    JSCLASS_HAS_PRIVATE |
+        JSCLASS_HAS_RESERVED_SLOTS(Debugger::JSSLOT_DEBUG_COUNT),
+    &classOps_};
+
+static Debugger* Debugger_fromThisValue(JSContext* cx, const CallArgs& args,
+                                        const char* fnname) {
+  JSObject* thisobj = RequireObject(cx, args.thisv());
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerInstanceObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger", fnname,
+                              thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  // Forbid Debugger.prototype, which is of the Debugger JSClass but isn't
+  // really a Debugger object. The prototype object is distinguished by
+  // having a nullptr private value.
+  Debugger* dbg = Debugger::fromJSObject(thisobj);
+  if (!dbg) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger", fnname,
+                              "prototype object");
+  }
+  return dbg;
+}
+
+struct MOZ_STACK_CLASS Debugger::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  Debugger* dbg;
+
+  CallData(JSContext* cx, const CallArgs& args, Debugger* dbg)
+      : cx(cx), args(args), dbg(dbg) {}
+
+  bool getOnDebuggerStatement();
+  bool setOnDebuggerStatement();
+  bool getOnExceptionUnwind();
+  bool setOnExceptionUnwind();
+  bool getOnNewScript();
+  bool setOnNewScript();
+  bool getOnEnterFrame();
+  bool setOnEnterFrame();
+  bool getOnNativeCall();
+  bool setOnNativeCall();
+  bool getOnNewGlobalObject();
+  bool setOnNewGlobalObject();
+  bool getOnNewPromise();
+  bool setOnNewPromise();
+  bool getOnPromiseSettled();
+  bool setOnPromiseSettled();
+  bool getUncaughtExceptionHook();
+  bool setUncaughtExceptionHook();
+  bool getAllowUnobservedAsmJS();
+  bool setAllowUnobservedAsmJS();
+  bool getCollectCoverageInfo();
+  bool setCollectCoverageInfo();
+  bool getMemory();
+  bool addDebuggee();
+  bool addAllGlobalsAsDebuggees();
+  bool removeDebuggee();
+  bool removeAllDebuggees();
+  bool hasDebuggee();
+  bool getDebuggees();
+  bool getNewestFrame();
+  bool clearAllBreakpoints();
+  bool findScripts();
+  bool findSources();
+  bool findObjects();
+  bool findAllGlobals();
+  bool findSourceURLs();
+  bool makeGlobalObjectReference();
+  bool adoptDebuggeeValue();
+  bool adoptFrame();
+  bool adoptSource();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <Debugger::CallData::Method MyMethod>
+/* static */
+bool Debugger::CallData::ToNative(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  Debugger* dbg = Debugger_fromThisValue(cx, args, "method");
+  if (!dbg) {
+    return false;
+  }
+
+  CallData data(cx, args, dbg);
+  return (data.*MyMethod)();
+}
+
+/* static */
+bool Debugger::getHookImpl(JSContext* cx, const CallArgs& args, Debugger& dbg,
+                           Hook which) {
+  MOZ_ASSERT(which >= 0 && which < HookCount);
+  args.rval().set(dbg.object->getReservedSlot(JSSLOT_DEBUG_HOOK_START + which));
+  return true;
+}
+
+/* static */
+bool Debugger::setHookImpl(JSContext* cx, const CallArgs& args, Debugger& dbg,
+                           Hook which) {
+  MOZ_ASSERT(which >= 0 && which < HookCount);
+  if (!args.requireAtLeast(cx, "Debugger.setHook", 1)) {
+    return false;
+  }
+  if (args[0].isObject()) {
+    if (!args[0].toObject().isCallable()) {
+      return ReportIsNotFunction(cx, args[0], args.length() - 1);
+    }
+  } else if (!args[0].isUndefined()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_CALLABLE_OR_UNDEFINED);
+    return false;
+  }
+  uint32_t slot = JSSLOT_DEBUG_HOOK_START + which;
+  RootedValue oldHook(cx, dbg.object->getReservedSlot(slot));
+  dbg.object->setReservedSlot(slot, args[0]);
+  if (hookObservesAllExecution(which)) {
+    if (!dbg.updateObservesAllExecutionOnDebuggees(
+            cx, dbg.observesAllExecution())) {
+      dbg.object->setReservedSlot(slot, oldHook);
+      return false;
+    }
+  }
+
+  Rooted<DebuggerDebuggeeLink*> debuggeeLink(cx, dbg.getDebuggeeLink());
+  if (dbg.hasAnyLiveHooks()) {
+    debuggeeLink->setLinkSlot(dbg);
+  } else {
+    debuggeeLink->clearLinkSlot();
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+/* static */
+bool Debugger::getGarbageCollectionHook(JSContext* cx, const CallArgs& args,
+                                        Debugger& dbg) {
+  return getHookImpl(cx, args, dbg, OnGarbageCollection);
+}
+
+/* static */
+bool Debugger::setGarbageCollectionHook(JSContext* cx, const CallArgs& args,
+                                        Debugger& dbg) {
+  Rooted<JSObject*> oldHook(cx, dbg.getHook(OnGarbageCollection));
+
+  if (!setHookImpl(cx, args, dbg, OnGarbageCollection)) {
+    // We want to maintain the invariant that the hook is always set when the
+    // Debugger is in the runtime's list, and vice-versa, so if we return early
+    // and don't adjust the watcher list below, we need to be sure that the
+    // hook didn't change.
+    MOZ_ASSERT(dbg.getHook(OnGarbageCollection) == oldHook);
+    return false;
+  }
+
+  // Add or remove ourselves from the runtime's list of Debuggers that care
+  // about garbage collection.
+  JSObject* newHook = dbg.getHook(OnGarbageCollection);
+  if (!oldHook && newHook) {
+    cx->runtime()->onGarbageCollectionWatchers().pushBack(&dbg);
+  } else if (oldHook && !newHook) {
+    cx->runtime()->onGarbageCollectionWatchers().remove(&dbg);
+  }
+
+  return true;
+}
+
+bool Debugger::CallData::getOnDebuggerStatement() {
+  return getHookImpl(cx, args, *dbg, OnDebuggerStatement);
+}
+
+bool Debugger::CallData::setOnDebuggerStatement() {
+  return setHookImpl(cx, args, *dbg, OnDebuggerStatement);
+}
+
+bool Debugger::CallData::getOnExceptionUnwind() {
+  return getHookImpl(cx, args, *dbg, OnExceptionUnwind);
+}
+
+bool Debugger::CallData::setOnExceptionUnwind() {
+  return setHookImpl(cx, args, *dbg, OnExceptionUnwind);
+}
+
+bool Debugger::CallData::getOnNewScript() {
+  return getHookImpl(cx, args, *dbg, OnNewScript);
+}
+
+bool Debugger::CallData::setOnNewScript() {
+  return setHookImpl(cx, args, *dbg, OnNewScript);
+}
+
+bool Debugger::CallData::getOnNewPromise() {
+  return getHookImpl(cx, args, *dbg, OnNewPromise);
+}
+
+bool Debugger::CallData::setOnNewPromise() {
+  return setHookImpl(cx, args, *dbg, OnNewPromise);
+}
+
+bool Debugger::CallData::getOnPromiseSettled() {
+  return getHookImpl(cx, args, *dbg, OnPromiseSettled);
+}
+
+bool Debugger::CallData::setOnPromiseSettled() {
+  return setHookImpl(cx, args, *dbg, OnPromiseSettled);
+}
+
+bool Debugger::CallData::getOnEnterFrame() {
+  return getHookImpl(cx, args, *dbg, OnEnterFrame);
+}
+
+bool Debugger::CallData::setOnEnterFrame() {
+  return setHookImpl(cx, args, *dbg, OnEnterFrame);
+}
+
+bool Debugger::CallData::getOnNativeCall() {
+  return getHookImpl(cx, args, *dbg, OnNativeCall);
+}
+
+bool Debugger::CallData::setOnNativeCall() {
+  return setHookImpl(cx, args, *dbg, OnNativeCall);
+}
+
+bool Debugger::CallData::getOnNewGlobalObject() {
+  return getHookImpl(cx, args, *dbg, OnNewGlobalObject);
+}
+
+bool Debugger::CallData::setOnNewGlobalObject() {
+  RootedObject oldHook(cx, dbg->getHook(OnNewGlobalObject));
+
+  if (!setHookImpl(cx, args, *dbg, OnNewGlobalObject)) {
+    return false;
+  }
+
+  // Add or remove ourselves from the runtime's list of Debuggers that care
+  // about new globals.
+  JSObject* newHook = dbg->getHook(OnNewGlobalObject);
+  if (!oldHook && newHook) {
+    cx->runtime()->onNewGlobalObjectWatchers().pushBack(dbg);
+  } else if (oldHook && !newHook) {
+    cx->runtime()->onNewGlobalObjectWatchers().remove(dbg);
+  }
+
+  return true;
+}
+
+bool Debugger::CallData::getUncaughtExceptionHook() {
+  args.rval().setObjectOrNull(dbg->uncaughtExceptionHook);
+  return true;
+}
+
+bool Debugger::CallData::setUncaughtExceptionHook() {
+  if (!args.requireAtLeast(cx, "Debugger.set uncaughtExceptionHook", 1)) {
+    return false;
+  }
+  if (!args[0].isNull() &&
+      (!args[0].isObject() || !args[0].toObject().isCallable())) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_ASSIGN_FUNCTION_OR_NULL,
+                              "uncaughtExceptionHook");
+    return false;
+  }
+  dbg->uncaughtExceptionHook = args[0].toObjectOrNull();
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::getAllowUnobservedAsmJS() {
+  args.rval().setBoolean(dbg->allowUnobservedAsmJS);
+  return true;
+}
+
+bool Debugger::CallData::setAllowUnobservedAsmJS() {
+  if (!args.requireAtLeast(cx, "Debugger.set allowUnobservedAsmJS", 1)) {
+    return false;
+  }
+  dbg->allowUnobservedAsmJS = ToBoolean(args[0]);
+
+  for (WeakGlobalObjectSet::Range r = dbg->debuggees.all(); !r.empty();
+       r.popFront()) {
+    GlobalObject* global = r.front();
+    Realm* realm = global->realm();
+    realm->updateDebuggerObservesAsmJS();
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::getCollectCoverageInfo() {
+  args.rval().setBoolean(dbg->collectCoverageInfo);
+  return true;
+}
+
+bool Debugger::CallData::setCollectCoverageInfo() {
+  if (!args.requireAtLeast(cx, "Debugger.set collectCoverageInfo", 1)) {
+    return false;
+  }
+  dbg->collectCoverageInfo = ToBoolean(args[0]);
+
+  IsObserving observing = dbg->collectCoverageInfo ? Observing : NotObserving;
+  if (!dbg->updateObservesCoverageOnDebuggees(cx, observing)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::getMemory() {
+  Value memoryValue =
+      dbg->object->getReservedSlot(JSSLOT_DEBUG_MEMORY_INSTANCE);
+
+  if (!memoryValue.isObject()) {
+    RootedObject memory(cx, DebuggerMemory::create(cx, dbg));
+    if (!memory) {
+      return false;
+    }
+    memoryValue = ObjectValue(*memory);
+  }
+
+  args.rval().set(memoryValue);
+  return true;
+}
+
+/*
+ * Given a value used to designate a global (there's quite a variety; see the
+ * docs), return the actual designee.
+ *
+ * Note that this does not check whether the designee is marked "invisible to
+ * Debugger" or not; different callers need to handle invisible-to-Debugger
+ * globals in different ways.
+ */
+GlobalObject* Debugger::unwrapDebuggeeArgument(JSContext* cx, const Value& v) {
+  if (!v.isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_UNEXPECTED_TYPE, "argument",
+                              "not a global object");
+    return nullptr;
+  }
+
+  RootedObject obj(cx, &v.toObject());
+
+  // If it's a Debugger.Object belonging to this debugger, dereference that.
+  if (obj->getClass() == &DebuggerObject::class_) {
+    RootedValue rv(cx, v);
+    if (!unwrapDebuggeeValue(cx, &rv)) {
+      return nullptr;
+    }
+    obj = &rv.toObject();
+  }
+
+  // If we have a cross-compartment wrapper, dereference as far as is secure.
+  //
+  // Since we're dealing with globals, we may have a WindowProxy here.  So we
+  // have to make sure to do a dynamic unwrap, and we want to unwrap the
+  // WindowProxy too, if we have one.
+  obj = CheckedUnwrapDynamic(obj, cx, /* stopAtWindowProxy = */ false);
+  if (!obj) {
+    ReportAccessDenied(cx);
+    return nullptr;
+  }
+
+  // If that didn't produce a global object, it's an error.
+  if (!obj->is<GlobalObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_UNEXPECTED_TYPE, "argument",
+                              "not a global object");
+    return nullptr;
+  }
+
+  return &obj->as<GlobalObject>();
+}
+
+bool Debugger::CallData::addDebuggee() {
+  if (!args.requireAtLeast(cx, "Debugger.addDebuggee", 1)) {
+    return false;
+  }
+  Rooted<GlobalObject*> global(cx, dbg->unwrapDebuggeeArgument(cx, args[0]));
+  if (!global) {
+    return false;
+  }
+
+  if (!dbg->addDebuggeeGlobal(cx, global)) {
+    return false;
+  }
+
+  RootedValue v(cx, ObjectValue(*global));
+  if (!dbg->wrapDebuggeeValue(cx, &v)) {
+    return false;
+  }
+  args.rval().set(v);
+  return true;
+}
+
+bool Debugger::CallData::addAllGlobalsAsDebuggees() {
+  for (CompartmentsIter comp(cx->runtime()); !comp.done(); comp.next()) {
+    if (comp == dbg->object->compartment()) {
+      continue;
+    }
+    for (RealmsInCompartmentIter r(comp); !r.done(); r.next()) {
+      if (r->creationOptions().invisibleToDebugger()) {
+        continue;
+      }
+      r->compartment()->gcState.scheduledForDestruction = false;
+      GlobalObject* global = r->maybeGlobal();
+      if (global) {
+        Rooted<GlobalObject*> rg(cx, global);
+        if (!dbg->addDebuggeeGlobal(cx, rg)) {
+          return false;
+        }
+      }
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::removeDebuggee() {
+  if (!args.requireAtLeast(cx, "Debugger.removeDebuggee", 1)) {
+    return false;
+  }
+  Rooted<GlobalObject*> global(cx, dbg->unwrapDebuggeeArgument(cx, args[0]));
+  if (!global) {
+    return false;
+  }
+
+  ExecutionObservableRealms obs(cx);
+
+  if (dbg->debuggees.has(global)) {
+    dbg->removeDebuggeeGlobal(cx->runtime()->defaultFreeOp(), global, nullptr,
+                              FromSweep::No);
+
+    // Only update the realm if there are no Debuggers left, as it's
+    // expensive to check if no other Debugger has a live script or frame
+    // hook on any of the current on-stack debuggee frames.
+    if (global->getDebuggers().empty() && !obs.add(global->realm())) {
+      return false;
+    }
+    if (!updateExecutionObservability(cx, obs, NotObserving)) {
+      return false;
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::removeAllDebuggees() {
+  ExecutionObservableRealms obs(cx);
+
+  for (WeakGlobalObjectSet::Enum e(dbg->debuggees); !e.empty(); e.popFront()) {
+    Rooted<GlobalObject*> global(cx, e.front());
+    dbg->removeDebuggeeGlobal(cx->runtime()->defaultFreeOp(), global, &e,
+                              FromSweep::No);
+
+    // See note about adding to the observable set in removeDebuggee.
+    if (global->getDebuggers().empty() && !obs.add(global->realm())) {
+      return false;
+    }
+  }
+
+  if (!updateExecutionObservability(cx, obs, NotObserving)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool Debugger::CallData::hasDebuggee() {
+  if (!args.requireAtLeast(cx, "Debugger.hasDebuggee", 1)) {
+    return false;
+  }
+  GlobalObject* global = dbg->unwrapDebuggeeArgument(cx, args[0]);
+  if (!global) {
+    return false;
+  }
+  args.rval().setBoolean(!!dbg->debuggees.lookup(global));
+  return true;
+}
+
+bool Debugger::CallData::getDebuggees() {
+  // Obtain the list of debuggees before wrapping each debuggee, as a GC could
+  // update the debuggees set while we are iterating it.
+  unsigned count = dbg->debuggees.count();
+  RootedValueVector debuggees(cx);
+  if (!debuggees.resize(count)) {
+    return false;
+  }
+  unsigned i = 0;
+  {
+    JS::AutoCheckCannotGC nogc;
+    for (WeakGlobalObjectSet::Enum e(dbg->debuggees); !e.empty();
+         e.popFront()) {
+      debuggees[i++].setObject(*e.front().get());
+    }
+  }
+
+  RootedArrayObject arrobj(cx, NewDenseFullyAllocatedArray(cx, count));
+  if (!arrobj) {
+    return false;
+  }
+  arrobj->ensureDenseInitializedLength(0, count);
+  for (i = 0; i < count; i++) {
+    RootedValue v(cx, debuggees[i]);
+    if (!dbg->wrapDebuggeeValue(cx, &v)) {
+      return false;
+    }
+    arrobj->setDenseElement(i, v);
+  }
+
+  args.rval().setObject(*arrobj);
+  return true;
+}
+
+bool Debugger::CallData::getNewestFrame() {
+  // Since there may be multiple contexts, use AllFramesIter.
+  for (AllFramesIter i(cx); !i.done(); ++i) {
+    if (dbg->observesFrame(i)) {
+      // Ensure that Ion frames are rematerialized. Only rematerialized
+      // Ion frames may be used as AbstractFramePtrs.
+      if (i.isIon() && !i.ensureHasRematerializedFrame(cx)) {
+        return false;
+      }
+      AbstractFramePtr frame = i.abstractFramePtr();
+      FrameIter iter(i.activation()->cx());
+      while (!iter.hasUsableAbstractFramePtr() ||
+             iter.abstractFramePtr() != frame) {
+        ++iter;
+      }
+      return dbg->getFrame(cx, iter, args.rval());
+    }
+  }
+  args.rval().setNull();
+  return true;
+}
+
+bool Debugger::CallData::clearAllBreakpoints() {
+  JSFreeOp* fop = cx->defaultFreeOp();
+  Breakpoint* nextbp;
+  for (Breakpoint* bp = dbg->firstBreakpoint(); bp; bp = nextbp) {
+    nextbp = bp->nextInDebugger();
+
+    bp->remove(fop);
+  }
+  MOZ_ASSERT(!dbg->firstBreakpoint());
+
+  return true;
+}
+
+/* static */
+bool Debugger::construct(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  // Check that the arguments, if any, are cross-compartment wrappers.
+  for (unsigned i = 0; i < args.length(); i++) {
+    JSObject* argobj = RequireObject(cx, args[i]);
+    if (!argobj) {
+      return false;
+    }
+    if (!argobj->is<CrossCompartmentWrapperObject>()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_CCW_REQUIRED, "Debugger");
+      return false;
+    }
+  }
+
+  // Get Debugger.prototype.
+  RootedValue v(cx);
+  RootedObject callee(cx, &args.callee());
+  if (!GetProperty(cx, callee, callee, cx->names().prototype, &v)) {
+    return false;
+  }
+  RootedNativeObject proto(cx, &v.toObject().as<NativeObject>());
+  MOZ_ASSERT(proto->is<DebuggerInstanceObject>());
+
+  // Make the new Debugger object. Each one has a reference to
+  // Debugger.{Frame,Object,Script,Memory}.prototype in reserved slots. The
+  // rest of the reserved slots are for hooks; they default to undefined.
+  Rooted<DebuggerInstanceObject*> obj(
+      cx, NewTenuredObjectWithGivenProto<DebuggerInstanceObject>(cx, proto));
+  if (!obj) {
+    return false;
+  }
+  for (unsigned slot = JSSLOT_DEBUG_PROTO_START; slot < JSSLOT_DEBUG_PROTO_STOP;
+       slot++) {
+    obj->setReservedSlot(slot, proto->getReservedSlot(slot));
+  }
+  obj->setReservedSlot(JSSLOT_DEBUG_MEMORY_INSTANCE, NullValue());
+
+  RootedNativeObject livenessLink(
+      cx, NewObjectWithGivenProto<DebuggerDebuggeeLink>(cx, nullptr));
+  if (!livenessLink) {
+    return false;
+  }
+  obj->setReservedSlot(JSSLOT_DEBUG_DEBUGGEE_LINK, ObjectValue(*livenessLink));
+
+  Debugger* debugger;
+  {
+    // Construct the underlying C++ object.
+    auto dbg = cx->make_unique<Debugger>(cx, obj.get());
+    if (!dbg) {
+      return false;
+    }
+
+    // The object owns the released pointer.
+    debugger = dbg.release();
+    InitObjectPrivate(obj, debugger, MemoryUse::Debugger);
+  }
+
+  // Add the initial debuggees, if any.
+  for (unsigned i = 0; i < args.length(); i++) {
+    JSObject& wrappedObj =
+        args[i].toObject().as<ProxyObject>().private_().toObject();
+    Rooted<GlobalObject*> debuggee(cx, &wrappedObj.nonCCWGlobal());
+    if (!debugger->addDebuggeeGlobal(cx, debuggee)) {
+      return false;
+    }
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+bool Debugger::addDebuggeeGlobal(JSContext* cx, Handle<GlobalObject*> global) {
+  if (debuggees.has(global)) {
+    return true;
+  }
+
+  // Callers should generally be unable to get a reference to a debugger-
+  // invisible global in order to pass it to addDebuggee. But this is possible
+  // with certain testing aides we expose in the shell, so just make addDebuggee
+  // throw in that case.
+  Realm* debuggeeRealm = global->realm();
+  if (debuggeeRealm->creationOptions().invisibleToDebugger()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_CANT_DEBUG_GLOBAL);
+    return false;
+  }
+
+  // Debugger and debuggee must be in different compartments.
+  if (debuggeeRealm->compartment() == object->compartment()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_SAME_COMPARTMENT);
+    return false;
+  }
+
+  // Check for cycles. If global's realm is reachable from this Debugger
+  // object's realm by following debuggee-to-debugger links, then adding
+  // global would create a cycle. (Typically nobody is debugging the
+  // debugger, in which case we zip through this code without looping.)
+  Vector<Realm*> visited(cx);
+  if (!visited.append(object->realm())) {
+    return false;
+  }
+  for (size_t i = 0; i < visited.length(); i++) {
+    Realm* realm = visited[i];
+    if (realm == debuggeeRealm) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_DEBUG_LOOP);
+      return false;
+    }
+
+    // Find all realms containing debuggers debugging realm's global object.
+    // Add those realms to visited.
+    if (realm->isDebuggee()) {
+      for (Realm::DebuggerVectorEntry& entry : realm->getDebuggers()) {
+        Realm* next = entry.dbg->object->realm();
+        if (std::find(visited.begin(), visited.end(), next) == visited.end()) {
+          if (!visited.append(next)) {
+            return false;
+          }
+        }
+      }
+    }
+  }
+
+  // For global to become this js::Debugger's debuggee:
+  //
+  // 1. this js::Debugger must be in global->getDebuggers(),
+  // 2. global must be in this->debuggees,
+  // 3. the debuggee's zone must be in this->debuggeeZones,
+  // 4. if we are tracking allocations, the SavedStacksMetadataBuilder must be
+  //    installed for this realm, and
+  // 5. Realm::isDebuggee()'s bit must be set.
+  //
+  // All five indications must be kept consistent.
+
+  AutoRealm ar(cx, global);
+  Zone* zone = global->zone();
+
+  RootedObject debuggeeLink(cx, getDebuggeeLink());
+  if (!cx->compartment()->wrap(cx, &debuggeeLink)) {
+    return false;
+  }
+
+  // (1)
+  auto& globalDebuggers = global->getDebuggers();
+  if (!globalDebuggers.append(Realm::DebuggerVectorEntry(this, debuggeeLink))) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+  auto globalDebuggersGuard = MakeScopeExit([&] { globalDebuggers.popBack(); });
+
+  // (2)
+  if (!debuggees.put(global)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+  auto debuggeesGuard = MakeScopeExit([&] { debuggees.remove(global); });
+
+  bool addingZoneRelation = !debuggeeZones.has(zone);
+
+  // (3)
+  if (addingZoneRelation && !debuggeeZones.put(zone)) {
+    ReportOutOfMemory(cx);
+    return false;
+  }
+  auto debuggeeZonesGuard = MakeScopeExit([&] {
+    if (addingZoneRelation) {
+      debuggeeZones.remove(zone);
+    }
+  });
+
+  // (4)
+  if (trackingAllocationSites &&
+      !Debugger::addAllocationsTracking(cx, global)) {
+    return false;
+  }
+
+  auto allocationsTrackingGuard = MakeScopeExit([&] {
+    if (trackingAllocationSites) {
+      Debugger::removeAllocationsTracking(*global);
+    }
+  });
+
+  // (5)
+  AutoRestoreRealmDebugMode debugModeGuard(debuggeeRealm);
+  debuggeeRealm->setIsDebuggee();
+  debuggeeRealm->updateDebuggerObservesAsmJS();
+  debuggeeRealm->updateDebuggerObservesCoverage();
+  if (observesAllExecution() &&
+      !ensureExecutionObservabilityOfRealm(cx, debuggeeRealm)) {
+    return false;
+  }
+
+  globalDebuggersGuard.release();
+  debuggeesGuard.release();
+  debuggeeZonesGuard.release();
+  allocationsTrackingGuard.release();
+  debugModeGuard.release();
+  return true;
+}
+
+void Debugger::recomputeDebuggeeZoneSet() {
+  AutoEnterOOMUnsafeRegion oomUnsafe;
+  debuggeeZones.clear();
+  for (auto range = debuggees.all(); !range.empty(); range.popFront()) {
+    if (!debuggeeZones.put(range.front().unbarrieredGet()->zone())) {
+      oomUnsafe.crash("Debugger::removeDebuggeeGlobal");
+    }
+  }
+}
+
+template <typename T, typename AP>
+static T* findDebuggerInVector(Debugger* dbg, Vector<T, 0, AP>* vec) {
+  T* p;
+  for (p = vec->begin(); p != vec->end(); p++) {
+    if (p->dbg == dbg) {
+      break;
+    }
+  }
+  MOZ_ASSERT(p != vec->end());
+  return p;
+}
+
+void Debugger::removeDebuggeeGlobal(JSFreeOp* fop, GlobalObject* global,
+                                    WeakGlobalObjectSet::Enum* debugEnum,
+                                    FromSweep fromSweep) {
+  // The caller might have found global by enumerating this->debuggees; if
+  // so, use HashSet::Enum::removeFront rather than HashSet::remove below,
+  // to avoid invalidating the live enumerator.
+  MOZ_ASSERT(debuggees.has(global));
+  MOZ_ASSERT(debuggeeZones.has(global->zone()));
+  MOZ_ASSERT_IF(debugEnum, debugEnum->front().unbarrieredGet() == global);
+
+  // Clear this global's generators from generatorFrames as well.
+  //
+  // This method can be called either from script (dbg.removeDebuggee) or during
+  // GC sweeping, because the Debugger, debuggee global, or both are being GC'd.
+  //
+  // When called from script, it's okay to iterate over generatorFrames and
+  // touch its keys and values (even when an incremental GC is in progress).
+  // When called from GC, it's not okay; the keys and values may be dying. But
+  // in that case, we can actually just skip the loop entirely! If the Debugger
+  // is going away, it doesn't care about the state of its generatorFrames
+  // table, and the Debugger.Frame finalizer will fix up the generator observer
+  // counts.
+  if (fromSweep == FromSweep::No) {
+    for (GeneratorWeakMap::Enum e(generatorFrames); !e.empty(); e.popFront()) {
+      AbstractGeneratorObject& genObj = *e.front().key();
+      if (&genObj.global() == global) {
+        terminateDebuggerFrame(fop, this, e.front().value(), NullFramePtr(),
+                               nullptr, &e);
+      }
+    }
+  }
+
+  for (FrameMap::Enum e(frames); !e.empty(); e.popFront()) {
+    AbstractFramePtr frame = e.front().key();
+    if (frame.hasGlobal(global)) {
+      terminateDebuggerFrame(fop, this, e.front().value(), frame, &e);
+    }
+  }
+
+  auto& globalDebuggersVector = global->getDebuggers();
+
+  // The relation must be removed from up to three places:
+  // globalDebuggersVector and debuggees for sure, and possibly the
+  // compartment's debuggee set.
+  //
+  // The debuggee zone set is recomputed on demand. This avoids refcounting
+  // and in practice we have relatively few debuggees that tend to all be in
+  // the same zone. If after recomputing the debuggee zone set, this global's
+  // zone is not in the set, then we must remove ourselves from the zone's
+  // vector of observing debuggers.
+  globalDebuggersVector.erase(
+      findDebuggerInVector(this, &globalDebuggersVector));
+
+  if (debugEnum) {
+    debugEnum->removeFront();
+  } else {
+    debuggees.remove(global);
+  }
+
+  recomputeDebuggeeZoneSet();
+
+  // Remove all breakpoints for the debuggee.
+  Breakpoint* nextbp;
+  for (Breakpoint* bp = firstBreakpoint(); bp; bp = nextbp) {
+    nextbp = bp->nextInDebugger();
+
+    if (bp->site->realm() == global->realm()) {
+      bp->remove(fop);
+    }
+  }
+  MOZ_ASSERT_IF(debuggees.empty(), !firstBreakpoint());
+
+  // If we are tracking allocation sites, we need to remove the object
+  // metadata callback from this global's realm.
+  if (trackingAllocationSites) {
+    Debugger::removeAllocationsTracking(*global);
+  }
+
+  if (global->realm()->getDebuggers().empty()) {
+    global->realm()->unsetIsDebuggee();
+  } else {
+    global->realm()->updateDebuggerObservesAllExecution();
+    global->realm()->updateDebuggerObservesAsmJS();
+    global->realm()->updateDebuggerObservesCoverage();
+  }
+}
+
+class MOZ_STACK_CLASS Debugger::QueryBase {
+ protected:
+  QueryBase(JSContext* cx, Debugger* dbg)
+      : cx(cx),
+        debugger(dbg),
+        iterMarker(&cx->runtime()->gc),
+        realms(cx->zone()) {}
+
+  // The context in which we should do our work.
+  JSContext* cx;
+
+  // The debugger for which we conduct queries.
+  Debugger* debugger;
+
+  // Require the set of realms to stay fixed while the query is alive.
+  gc::AutoEnterIteration iterMarker;
+
+  using RealmSet = HashSet<Realm*, DefaultHasher<Realm*>, ZoneAllocPolicy>;
+
+  // A script must be in one of these realms to match the query.
+  RealmSet realms;
+
+  // Indicates whether OOM has occurred while matching.
+  bool oom = false;
+
+  bool addRealm(Realm* realm) { return realms.put(realm); }
+
+  // Arrange for this query to match only scripts that run in |global|.
+  bool matchSingleGlobal(GlobalObject* global) {
+    MOZ_ASSERT(realms.count() == 0);
+    if (!addRealm(global->realm())) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+    return true;
+  }
+
+  // Arrange for this ScriptQuery to match all scripts running in debuggee
+  // globals.
+  bool matchAllDebuggeeGlobals() {
+    MOZ_ASSERT(realms.count() == 0);
+    // Build our realm set from the debugger's set of debuggee globals.
+    for (WeakGlobalObjectSet::Range r = debugger->debuggees.all(); !r.empty();
+         r.popFront()) {
+      if (!addRealm(r.front()->realm())) {
+        ReportOutOfMemory(cx);
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+/*
+ * A class for parsing 'findScripts' query arguments and searching for
+ * scripts that match the criteria they represent.
+ */
+class MOZ_STACK_CLASS Debugger::ScriptQuery : public Debugger::QueryBase {
+ public:
+  /* Construct a ScriptQuery to use matching scripts for |dbg|. */
+  ScriptQuery(JSContext* cx, Debugger* dbg)
+      : QueryBase(cx, dbg),
+        url(cx),
+        displayURLString(cx),
+        source(cx, AsVariant(static_cast<ScriptSourceObject*>(nullptr))),
+        scriptVector(cx, BaseScriptVector(cx)),
+        partialMatchVector(cx, BaseScriptVector(cx)),
+        wasmInstanceVector(cx, WasmInstanceObjectVector(cx)) {}
+
+  /*
+   * Parse the query object |query|, and prepare to match only the scripts
+   * it specifies.
+   */
+  bool parseQuery(HandleObject query) {
+    // Check for a 'global' property, which limits the results to those
+    // scripts scoped to a particular global object.
+    RootedValue global(cx);
+    if (!GetProperty(cx, query, query, cx->names().global, &global)) {
+      return false;
+    }
+    if (global.isUndefined()) {
+      if (!matchAllDebuggeeGlobals()) {
+        return false;
+      }
+    } else {
+      GlobalObject* globalObject = debugger->unwrapDebuggeeArgument(cx, global);
+      if (!globalObject) {
+        return false;
+      }
+
+      // If the given global isn't a debuggee, just leave the set of
+      // acceptable globals empty; we'll return no scripts.
+      if (debugger->debuggees.has(globalObject)) {
+        if (!matchSingleGlobal(globalObject)) {
+          return false;
+        }
+      }
+    }
+
+    // Check for a 'url' property.
+    if (!GetProperty(cx, query, query, cx->names().url, &url)) {
+      return false;
+    }
+    if (!url.isUndefined() && !url.isString()) {
+      JS_ReportErrorNumberASCII(
+          cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+          "query object's 'url' property", "neither undefined nor a string");
+      return false;
+    }
+
+    // Check for a 'source' property
+    RootedValue debuggerSource(cx);
+    if (!GetProperty(cx, query, query, cx->names().source, &debuggerSource)) {
+      return false;
+    }
+    if (!debuggerSource.isUndefined()) {
+      if (!debuggerSource.isObject() ||
+          !debuggerSource.toObject().is<DebuggerSource>()) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_UNEXPECTED_TYPE,
+                                  "query object's 'source' property",
+                                  "not undefined nor a Debugger.Source object");
+        return false;
+      }
+
+      DebuggerSource& debuggerSourceObj =
+          debuggerSource.toObject().as<DebuggerSource>();
+
+      // The given source must have an owner. Otherwise, it's a
+      // Debugger.Source.prototype, which would match no scripts, and is
+      // probably a mistake.
+      if (!debuggerSourceObj.isInstance()) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_DEBUG_PROTO, "Debugger.Source",
+                                  "Debugger.Source");
+        return false;
+      }
+
+      // If it does have an owner, it should match the Debugger we're
+      // calling findScripts on. It would work fine even if it didn't,
+      // but mixing Debugger.Sources is probably a sign of confusion.
+      if (debuggerSourceObj.owner() != debugger) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_DEBUG_WRONG_OWNER, "Debugger.Source");
+        return false;
+      }
+
+      hasSource = true;
+      source = debuggerSourceObj.getReferent();
+    }
+
+    // Check for a 'displayURL' property.
+    RootedValue displayURL(cx);
+    if (!GetProperty(cx, query, query, cx->names().displayURL, &displayURL)) {
+      return false;
+    }
+    if (!displayURL.isUndefined() && !displayURL.isString()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_UNEXPECTED_TYPE,
+                                "query object's 'displayURL' property",
+                                "neither undefined nor a string");
+      return false;
+    }
+
+    if (displayURL.isString()) {
+      displayURLString = displayURL.toString()->ensureLinear(cx);
+      if (!displayURLString) {
+        return false;
+      }
+    }
+
+    // Check for a 'line' property.
+    RootedValue lineProperty(cx);
+    if (!GetProperty(cx, query, query, cx->names().line, &lineProperty)) {
+      return false;
+    }
+    if (lineProperty.isUndefined()) {
+      hasLine = false;
+    } else if (lineProperty.isNumber()) {
+      if (displayURL.isUndefined() && url.isUndefined() && !hasSource) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_QUERY_LINE_WITHOUT_URL);
+        return false;
+      }
+      double doubleLine = lineProperty.toNumber();
+      uint32_t uintLine = (uint32_t)doubleLine;
+      if (doubleLine <= 0 || uintLine != doubleLine) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_DEBUG_BAD_LINE);
+        return false;
+      }
+      hasLine = true;
+      line = uintLine;
+    } else {
+      JS_ReportErrorNumberASCII(
+          cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+          "query object's 'line' property", "neither undefined nor an integer");
+      return false;
+    }
+
+    // Check for an 'innermost' property.
+    PropertyName* innermostName = cx->names().innermost;
+    RootedValue innermostProperty(cx);
+    if (!GetProperty(cx, query, query, innermostName, &innermostProperty)) {
+      return false;
+    }
+    innermost = ToBoolean(innermostProperty);
+    if (innermost) {
+      // Technically, we need only check hasLine, but this is clearer.
+      if ((displayURL.isUndefined() && url.isUndefined() && !hasSource) ||
+          !hasLine) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_QUERY_INNERMOST_WITHOUT_LINE_URL);
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  /* Set up this ScriptQuery appropriately for a missing query argument. */
+  bool omittedQuery() {
+    url.setUndefined();
+    hasLine = false;
+    innermost = false;
+    displayURLString = nullptr;
+    return matchAllDebuggeeGlobals();
+  }
+
+  /*
+   * Search all relevant realms and the stack for scripts matching
+   * this query, and append the matching scripts to |scriptVector|.
+   */
+  bool findScripts() {
+    if (!prepareQuery()) {
+      return false;
+    }
+
+    Realm* singletonRealm = nullptr;
+    if (realms.count() == 1) {
+      singletonRealm = realms.all().front();
+    }
+
+    // Search each realm for debuggee scripts.
+    MOZ_ASSERT(scriptVector.empty());
+    MOZ_ASSERT(partialMatchVector.empty());
+    oom = false;
+    IterateScripts(cx, singletonRealm, this, considerScript);
+    if (oom) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+
+    // If we are filtering by line number, the lazy BaseScripts were not checked
+    // yet since they do not implement `GetScriptLineExtent`. Instead we revisit
+    // each result script and delazify its children and add any matching ones to
+    // the results list.
+    MOZ_ASSERT(hasLine || partialMatchVector.empty());
+    Rooted<BaseScript*> script(cx);
+    RootedFunction fun(cx);
+    while (!partialMatchVector.empty()) {
+      script = partialMatchVector.popCopy();
+
+      // As a performance optimization, we can skip scripts that are definitely
+      // out-of-bounds for the target line. This was checked before adding to
+      // the partialMatchVector, but the bound may have improved since then.
+      if (script->extent().sourceEnd <= sourceOffsetLowerBound) {
+        continue;
+      }
+
+      MOZ_ASSERT(script->isFunction());
+      MOZ_ASSERT(script->isReadyForDelazification());
+
+      fun = script->function();
+
+      // Delazify script.
+      JSScript* compiledScript = GetOrCreateFunctionScript(cx, fun);
+      if (!compiledScript) {
+        return false;
+      }
+
+      // If target line isn't in script, we are done with it.
+      if (!scriptIsLineMatch(compiledScript)) {
+        continue;
+      }
+
+      // Add script to results now that we've completed checks.
+      if (!scriptVector.append(compiledScript)) {
+        return false;
+      }
+
+      // If script was a leaf we are done with it. This is an optional
+      // optimization to avoid inspecting the `gcthings` list below.
+      if (!script->hasInnerFunctions()) {
+        continue;
+      }
+
+      // Now add inner scripts to `partialMatchVector` work list to determine if
+      // they are matches. Note that out IterateScripts callback ignored them
+      // already since they did not have a compiled parent at the time.
+      for (const JS::GCCellPtr& thing : script->gcthings()) {
+        if (!thing.is<JSObject>() || !thing.as<JSObject>().is<JSFunction>()) {
+          continue;
+        }
+        if (!thing.as<JSObject>().as<JSFunction>().hasBaseScript()) {
+          continue;
+        }
+        BaseScript* inner = thing.as<JSObject>().as<JSFunction>().baseScript();
+
+        if (!scriptIsPartialLineMatch(inner)) {
+          continue;
+        }
+
+        // Add the matching inner script to the back of the results queue
+        // where it will be processed recursively.
+        if (!partialMatchVector.append(inner)) {
+          return false;
+        }
+      }
+    }
+
+    // If this is an 'innermost' query, we want to filter the results again to
+    // only return the innermost script for each realm. To do this we build a
+    // hashmap to track innermost and then recreate the `scriptVector` with the
+    // results that remain in the hashmap.
+    if (innermost) {
+      using RealmToScriptMap =
+          GCHashMap<Realm*, BaseScript*, DefaultHasher<Realm*>>;
+
+      Rooted<RealmToScriptMap> innermostForRealm(cx);
+
+      // Visit each candidate script and find innermost in each realm.
+      for (BaseScript* script : scriptVector) {
+        Realm* realm = script->realm();
+        RealmToScriptMap::AddPtr p = innermostForRealm.lookupForAdd(realm);
+        if (p) {
+          // Is our newly found script deeper than the last one we found?
+          BaseScript* incumbent = p->value();
+          if (script->asJSScript()->innermostScope()->chainLength() >
+              incumbent->asJSScript()->innermostScope()->chainLength()) {
+            p->value() = script;
+          }
+        } else {
+          // This is the first matching script we've encountered for this
+          // realm, so it is thus the innermost such script.
+          if (!innermostForRealm.add(p, realm, script)) {
+            return false;
+          }
+        }
+      }
+
+      // Reset the results vector.
+      scriptVector.clear();
+
+      // Re-add only the innermost scripts to the results.
+      for (RealmToScriptMap::Range r = innermostForRealm.all(); !r.empty();
+           r.popFront()) {
+        if (!scriptVector.append(r.front().value())) {
+          return false;
+        }
+      }
+    }
+
+    // TODO: Until such time that wasm modules are real ES6 modules,
+    // unconditionally consider all wasm toplevel instance scripts.
+    for (WeakGlobalObjectSet::Range r = debugger->allDebuggees(); !r.empty();
+         r.popFront()) {
+      for (wasm::Instance* instance : r.front()->realm()->wasm.instances()) {
+        consider(instance->object());
+        if (oom) {
+          ReportOutOfMemory(cx);
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+
+  Handle<BaseScriptVector> foundScripts() const { return scriptVector; }
+
+  Handle<WasmInstanceObjectVector> foundWasmInstances() const {
+    return wasmInstanceVector;
+  }
+
+ private:
+  /* If this is a string, matching scripts have urls equal to it. */
+  RootedValue url;
+
+  /* url as a C string. */
+  UniqueChars urlCString;
+
+  /* If this is a string, matching scripts' sources have displayURLs equal to
+   * it. */
+  RootedLinearString displayURLString;
+
+  /*
+   * If this is a source referent, matching scripts will have sources equal
+   * to this instance. Ideally we'd use a Maybe here, but Maybe interacts
+   * very badly with Rooted's LIFO invariant.
+   */
+  bool hasSource = false;
+  Rooted<DebuggerSourceReferent> source;
+
+  /* True if the query contained a 'line' property. */
+  bool hasLine = false;
+
+  /* The line matching scripts must cover. */
+  uint32_t line = 0;
+
+  // As a performance optimization (and to avoid delazifying as many scripts),
+  // we would like to know the source offset of the target line.
+  //
+  // Since we do not have a simple way to compute this precisely, we instead
+  // track a lower-bound of the offset value. As we collect SourceExtent
+  // examples with (line,column) <-> sourceStart mappings, we can improve the
+  // bound. The target line is within the range [sourceOffsetLowerBound, Inf).
+  //
+  // NOTE: Using a SourceExtent for updating the bound happens independently of
+  //       if the script matches the target line or not in the in the end.
+  mutable uint32_t sourceOffsetLowerBound = 0;
+
+  /* True if the query has an 'innermost' property whose value is true. */
+  bool innermost = false;
+
+  /*
+   * Accumulate the scripts in an Rooted<BaseScriptVector> instead of creating
+   * the JS array as we go, because we mustn't allocate JS objects or GC while
+   * we use the CellIter.
+   */
+  Rooted<BaseScriptVector> scriptVector;
+
+  /*
+   * While in the CellIter we may find BaseScripts that need to be compiled
+   * before the query can be fully checked. Since we cannot compile while under
+   * CellIter we accumulate them here instead.
+   *
+   * This occurs when matching line numbers since `GetScriptLineExtent` cannot
+   * be computed without bytecode existing.
+   */
+  Rooted<BaseScriptVector> partialMatchVector;
+
+  /*
+   * Like above, but for wasm modules.
+   */
+  Rooted<WasmInstanceObjectVector> wasmInstanceVector;
+
+  /*
+   * Given that parseQuery or omittedQuery has been called, prepare to match
+   * scripts. Set urlCString and displayURLChars as appropriate.
+   */
+  bool prepareQuery() {
+    // Compute urlCString and displayURLChars, if a url or displayURL was
+    // given respectively.
+    if (url.isString()) {
+      urlCString = JS_EncodeStringToLatin1(cx, url.toString());
+      if (!urlCString) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  void updateSourceOffsetLowerBound(const SourceExtent& extent) {
+    // We trying to find the offset of (target-line, 0) so just ignore any
+    // extents on target line to keep things simple.
+    MOZ_ASSERT(extent.lineno <= line);
+    if (extent.lineno == line) {
+      return;
+    }
+
+    // The extent.sourceStart position is now definitely *before* the target
+    // line, so update sourceOffsetLowerBound if extent.sourceStart is a tighter
+    // bound.
+    if (extent.sourceStart > sourceOffsetLowerBound) {
+      sourceOffsetLowerBound = extent.sourceStart;
+    }
+  }
+
+  // A partial match is a script that starts before the target line, but may or
+  // may not end before it. If we can prove the script definitely ends before
+  // the target line, we may return false here.
+  bool scriptIsPartialLineMatch(BaseScript* script) {
+    const SourceExtent& extent = script->extent();
+
+    // Check that start of script is before or on target line.
+    if (extent.lineno > line) {
+      return false;
+    }
+
+    // Use the implicit (line, column) <-> sourceStart mapping from the
+    // SourceExtent to update our bounds on possible matches. We call this
+    // without knowing if the script is a match or not.
+    updateSourceOffsetLowerBound(script->extent());
+
+    // As an optional performance optimization, we rule out any script that ends
+    // before the lower-bound on where target line exists.
+    return extent.sourceEnd > sourceOffsetLowerBound;
+  }
+
+  // True if any part of script source is on the target line.
+  bool scriptIsLineMatch(JSScript* script) {
+    MOZ_ASSERT(scriptIsPartialLineMatch(script));
+
+    uint32_t lineCount = GetScriptLineExtent(script);
+    return (script->lineno() + lineCount > line);
+  }
+
+  static void considerScript(JSRuntime* rt, void* data, BaseScript* script,
+                             const JS::AutoRequireNoGC& nogc) {
+    ScriptQuery* self = static_cast<ScriptQuery*>(data);
+    self->consider(script, nogc);
+  }
+
+  template <typename T>
+  MOZ_MUST_USE bool commonFilter(T script, const JS::AutoRequireNoGC& nogc) {
+    if (urlCString) {
+      bool gotFilename = false;
+      if (script->filename() &&
+          strcmp(script->filename(), urlCString.get()) == 0) {
+        gotFilename = true;
+      }
+
+      bool gotSourceURL = false;
+      if (!gotFilename && script->scriptSource()->introducerFilename() &&
+          strcmp(script->scriptSource()->introducerFilename(),
+                 urlCString.get()) == 0) {
+        gotSourceURL = true;
+      }
+      if (!gotFilename && !gotSourceURL) {
+        return false;
+      }
+    }
+    if (displayURLString) {
+      if (!script->scriptSource() || !script->scriptSource()->hasDisplayURL()) {
+        return false;
+      }
+
+      const char16_t* s = script->scriptSource()->displayURL();
+      if (CompareChars(s, js_strlen(s), displayURLString) != 0) {
+        return false;
+      }
+    }
+    if (hasSource && !(source.is<ScriptSourceObject*>() &&
+                       source.as<ScriptSourceObject*>()->source() ==
+                           script->scriptSource())) {
+      return false;
+    }
+    return true;
+  }
+
+  /*
+   * If |script| matches this query, append it to |scriptVector|. Set |oom| if
+   * an out of memory condition occurred.
+   */
+  void consider(BaseScript* script, const JS::AutoRequireNoGC& nogc) {
+    if (oom || script->selfHosted()) {
+      return;
+    }
+
+    Realm* realm = script->realm();
+    if (!realms.has(realm)) {
+      return;
+    }
+
+    if (!commonFilter(script, nogc)) {
+      return;
+    }
+
+    bool partial = false;
+
+    if (hasLine) {
+      if (!scriptIsPartialLineMatch(script)) {
+        return;
+      }
+
+      if (script->hasBytecode()) {
+        // Check if line is within script (or any of its inner scripts).
+        if (!scriptIsLineMatch(script->asJSScript())) {
+          return;
+        }
+      } else {
+        // GetScriptLineExtent is not available on lazy scripts so instead to
+        // the partial match list for be compiled and reprocessed later. We only
+        // add scripts that are ready for delazification and they may in turn
+        // process their inner functions.
+        if (!script->isReadyForDelazification()) {
+          return;
+        }
+        partial = true;
+      }
+    }
+
+    // If innermost filter is required, we collect everything that matches the
+    // line number and filter at the end of `findScripts`.
+    MOZ_ASSERT_IF(innermost, hasLine);
+
+    Rooted<BaseScriptVector>& vec = partial ? partialMatchVector : scriptVector;
+    if (!vec.append(script)) {
+      oom = true;
+    }
+  }
+
+  /*
+   * If |instanceObject| matches this query, append it to |wasmInstanceVector|.
+   * Set |oom| if an out of memory condition occurred.
+   */
+  void consider(WasmInstanceObject* instanceObject) {
+    if (oom) {
+      return;
+    }
+
+    if (hasSource && source != AsVariant(instanceObject)) {
+      return;
+    }
+
+    if (!wasmInstanceVector.append(instanceObject)) {
+      oom = true;
+    }
+  }
+};
+
+bool Debugger::CallData::findScripts() {
+  ScriptQuery query(cx, dbg);
+
+  if (args.length() >= 1) {
+    RootedObject queryObject(cx, RequireObject(cx, args[0]));
+    if (!queryObject || !query.parseQuery(queryObject)) {
+      return false;
+    }
+  } else {
+    if (!query.omittedQuery()) {
+      return false;
+    }
+  }
+
+  if (!query.findScripts()) {
+    return false;
+  }
+
+  Handle<BaseScriptVector> scripts(query.foundScripts());
+  Handle<WasmInstanceObjectVector> wasmInstances(query.foundWasmInstances());
+
+  size_t resultLength = scripts.length() + wasmInstances.length();
+  RootedArrayObject result(cx, NewDenseFullyAllocatedArray(cx, resultLength));
+  if (!result) {
+    return false;
+  }
+
+  result->ensureDenseInitializedLength(0, resultLength);
+
+  for (size_t i = 0; i < scripts.length(); i++) {
+    JSObject* scriptObject = dbg->wrapScript(cx, scripts[i]);
+    if (!scriptObject) {
+      return false;
+    }
+    result->setDenseElement(i, ObjectValue(*scriptObject));
+  }
+
+  size_t wasmStart = scripts.length();
+  for (size_t i = 0; i < wasmInstances.length(); i++) {
+    JSObject* scriptObject = dbg->wrapWasmScript(cx, wasmInstances[i]);
+    if (!scriptObject) {
+      return false;
+    }
+    result->setDenseElement(wasmStart + i, ObjectValue(*scriptObject));
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+/*
+ * A class for searching sources for 'findSources'.
+ */
+class MOZ_STACK_CLASS Debugger::SourceQuery : public Debugger::QueryBase {
+ public:
+  using SourceSet = JS::GCHashSet<JSObject*, js::MovableCellHasher<JSObject*>,
+                                  ZoneAllocPolicy>;
+
+  SourceQuery(JSContext* cx, Debugger* dbg)
+      : QueryBase(cx, dbg), sources(cx, SourceSet(cx->zone())) {}
+
+  bool findSources() {
+    if (!matchAllDebuggeeGlobals()) {
+      return false;
+    }
+
+    Realm* singletonRealm = nullptr;
+    if (realms.count() == 1) {
+      singletonRealm = realms.all().front();
+    }
+
+    // Search each realm for debuggee scripts.
+    MOZ_ASSERT(sources.empty());
+    oom = false;
+    IterateScripts(cx, singletonRealm, this, considerScript);
+    if (oom) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+
+    // TODO: Until such time that wasm modules are real ES6 modules,
+    // unconditionally consider all wasm toplevel instance scripts.
+    for (WeakGlobalObjectSet::Range r = debugger->allDebuggees(); !r.empty();
+         r.popFront()) {
+      for (wasm::Instance* instance : r.front()->realm()->wasm.instances()) {
+        consider(instance->object());
+        if (oom) {
+          ReportOutOfMemory(cx);
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+
+  Handle<SourceSet> foundSources() const { return sources; }
+
+ private:
+  Rooted<SourceSet> sources;
+
+  static void considerScript(JSRuntime* rt, void* data, BaseScript* script,
+                             const JS::AutoRequireNoGC& nogc) {
+    SourceQuery* self = static_cast<SourceQuery*>(data);
+    self->consider(script, nogc);
+  }
+
+  void consider(BaseScript* script, const JS::AutoRequireNoGC& nogc) {
+    if (oom || script->selfHosted()) {
+      return;
+    }
+
+    Realm* realm = script->realm();
+    if (!realms.has(realm)) {
+      return;
+    }
+
+    ScriptSourceObject* source = script->sourceObject();
+    if (!sources.put(source)) {
+      oom = true;
+    }
+  }
+
+  void consider(WasmInstanceObject* instanceObject) {
+    if (oom) {
+      return;
+    }
+
+    if (!sources.put(instanceObject)) {
+      oom = true;
+    }
+  }
+};
+
+static inline DebuggerSourceReferent AsSourceReferent(JSObject* obj) {
+  if (obj->is<ScriptSourceObject>()) {
+    return AsVariant(&obj->as<ScriptSourceObject>());
+  }
+  return AsVariant(&obj->as<WasmInstanceObject>());
+}
+
+bool Debugger::CallData::findSources() {
+  SourceQuery query(cx, dbg);
+  if (!query.findSources()) {
+    return false;
+  }
+
+  Handle<SourceQuery::SourceSet> sources(query.foundSources());
+
+  size_t resultLength = sources.count();
+  RootedArrayObject result(cx, NewDenseFullyAllocatedArray(cx, resultLength));
+  if (!result) {
+    return false;
+  }
+
+  result->ensureDenseInitializedLength(0, resultLength);
+
+  size_t i = 0;
+  for (auto iter = sources.get().iter(); !iter.done(); iter.next()) {
+    Rooted<DebuggerSourceReferent> sourceReferent(cx,
+                                                  AsSourceReferent(iter.get()));
+    RootedObject sourceObject(cx, dbg->wrapVariantReferent(cx, sourceReferent));
+    if (!sourceObject) {
+      return false;
+    }
+    result->setDenseElement(i, ObjectValue(*sourceObject));
+    i++;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+/*
+ * A class for parsing 'findObjects' query arguments and searching for objects
+ * that match the criteria they represent.
+ */
+class MOZ_STACK_CLASS Debugger::ObjectQuery {
+ public:
+  /* Construct an ObjectQuery to use matching scripts for |dbg|. */
+  ObjectQuery(JSContext* cx, Debugger* dbg)
+      : objects(cx), cx(cx), dbg(dbg), className(cx) {}
+
+  /* The vector that we are accumulating results in. */
+  RootedObjectVector objects;
+
+  /* The set of debuggee compartments. */
+  JS::CompartmentSet debuggeeCompartments;
+
+  /*
+   * Parse the query object |query|, and prepare to match only the objects it
+   * specifies.
+   */
+  bool parseQuery(HandleObject query) {
+    // Check for the 'class' property
+    RootedValue cls(cx);
+    if (!GetProperty(cx, query, query, cx->names().class_, &cls)) {
+      return false;
+    }
+    if (!cls.isUndefined()) {
+      if (!cls.isString()) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                  JSMSG_UNEXPECTED_TYPE,
+                                  "query object's 'class' property",
+                                  "neither undefined nor a string");
+        return false;
+      }
+      JSLinearString* str = cls.toString()->ensureLinear(cx);
+      if (!str) {
+        return false;
+      }
+      if (!StringIsAscii(str)) {
+        JS_ReportErrorNumberASCII(
+            cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "query object's 'class' property",
+            "not a string containing only ASCII characters");
+        return false;
+      }
+      className = cls;
+    }
+    return true;
+  }
+
+  /* Set up this ObjectQuery appropriately for a missing query argument. */
+  void omittedQuery() { className.setUndefined(); }
+
+  /*
+   * Traverse the heap to find all relevant objects and add them to the
+   * provided vector.
+   */
+  bool findObjects() {
+    if (!prepareQuery()) {
+      return false;
+    }
+
+    for (WeakGlobalObjectSet::Range r = dbg->allDebuggees(); !r.empty();
+         r.popFront()) {
+      if (!debuggeeCompartments.put(r.front()->compartment())) {
+        ReportOutOfMemory(cx);
+        return false;
+      }
+    }
+
+    {
+      // We can't tolerate the GC moving things around while we're
+      // searching the heap. Check that nothing we do causes a GC.
+      Maybe<JS::AutoCheckCannotGC> maybeNoGC;
+      RootedObject dbgObj(cx, dbg->object);
+      JS::ubi::RootList rootList(cx, maybeNoGC);
+      if (!rootList.init(dbgObj)) {
+        ReportOutOfMemory(cx);
+        return false;
+      }
+
+      Traversal traversal(cx, *this, maybeNoGC.ref());
+      traversal.wantNames = false;
+
+      return traversal.addStart(JS::ubi::Node(&rootList)) &&
+             traversal.traverse();
+    }
+  }
+
+  /*
+   * |ubi::Node::BreadthFirst| interface.
+   */
+  class NodeData {};
+  using Traversal = JS::ubi::BreadthFirst<ObjectQuery>;
+  bool operator()(Traversal& traversal, JS::ubi::Node origin,
+                  const JS::ubi::Edge& edge, NodeData*, bool first) {
+    if (!first) {
+      return true;
+    }
+
+    JS::ubi::Node referent = edge.referent;
+
+    // Only follow edges within our set of debuggee compartments; we don't
+    // care about the heap's subgraphs outside of our debuggee compartments,
+    // so we abandon the referent. Either (1) there is not a path from this
+    // non-debuggee node back to a node in our debuggee compartments, and we
+    // don't need to follow edges to or from this node, or (2) there does
+    // exist some path from this non-debuggee node back to a node in our
+    // debuggee compartments. However, if that were true, then the incoming
+    // cross compartment edge back into a debuggee compartment is already
+    // listed as an edge in the RootList we started traversal with, and
+    // therefore we don't need to follow edges to or from this non-debuggee
+    // node.
+    JS::Compartment* comp = referent.compartment();
+    if (comp && !debuggeeCompartments.has(comp)) {
+      traversal.abandonReferent();
+      return true;
+    }
+
+    // If the referent has an associated realm and it's not a debuggee
+    // realm, skip it. Don't abandonReferent() here like above: realms
+    // within a compartment can reference each other without going through
+    // cross-compartment wrappers.
+    Realm* realm = referent.realm();
+    if (realm && !dbg->isDebuggeeUnbarriered(realm)) {
+      return true;
+    }
+
+    // If the referent is an object and matches our query's restrictions,
+    // add it to the vector accumulating results. Skip objects that should
+    // never be exposed to JS, like EnvironmentObjects and internal
+    // functions.
+
+    if (!referent.is<JSObject>() || referent.exposeToJS().isUndefined()) {
+      return true;
+    }
+
+    JSObject* obj = referent.as<JSObject>();
+
+    if (!className.isUndefined()) {
+      const char* objClassName = obj->getClass()->name;
+      if (strcmp(objClassName, classNameCString.get()) != 0) {
+        return true;
+      }
+    }
+
+    return objects.append(obj);
+  }
+
+ private:
+  /* The context in which we should do our work. */
+  JSContext* cx;
+
+  /* The debugger for which we conduct queries. */
+  Debugger* dbg;
+
+  /*
+   * If this is non-null, matching objects will have a class whose name is
+   * this property.
+   */
+  RootedValue className;
+
+  /* The className member, as a C string. */
+  UniqueChars classNameCString;
+
+  /*
+   * Given that either omittedQuery or parseQuery has been called, prepare the
+   * query for matching objects.
+   */
+  bool prepareQuery() {
+    if (className.isString()) {
+      classNameCString = JS_EncodeStringToASCII(cx, className.toString());
+      if (!classNameCString) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+};
+
+bool Debugger::CallData::findObjects() {
+  ObjectQuery query(cx, dbg);
+
+  if (args.length() >= 1) {
+    RootedObject queryObject(cx, RequireObject(cx, args[0]));
+    if (!queryObject || !query.parseQuery(queryObject)) {
+      return false;
+    }
+  } else {
+    query.omittedQuery();
+  }
+
+  if (!query.findObjects()) {
+    return false;
+  }
+
+  size_t length = query.objects.length();
+  RootedArrayObject result(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!result) {
+    return false;
+  }
+
+  result->ensureDenseInitializedLength(0, length);
+
+  for (size_t i = 0; i < length; i++) {
+    RootedValue debuggeeVal(cx, ObjectValue(*query.objects[i]));
+    if (!dbg->wrapDebuggeeValue(cx, &debuggeeVal)) {
+      return false;
+    }
+    result->setDenseElement(i, debuggeeVal);
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool Debugger::CallData::findAllGlobals() {
+  RootedObjectVector globals(cx);
+
+  {
+    // Accumulate the list of globals before wrapping them, because
+    // wrapping can GC and collect realms from under us, while iterating.
+    JS::AutoCheckCannotGC nogc;
+
+    for (RealmsIter r(cx->runtime()); !r.done(); r.next()) {
+      if (r->creationOptions().invisibleToDebugger()) {
+        continue;
+      }
+
+      if (!r->hasLiveGlobal()) {
+        continue;
+      }
+
+      if (JS::RealmBehaviorsRef(r).isNonLive()) {
+        continue;
+      }
+
+      r->compartment()->gcState.scheduledForDestruction = false;
+
+      GlobalObject* global = r->maybeGlobal();
+
+      if (cx->runtime()->isSelfHostingGlobal(global)) {
+        continue;
+      }
+
+      // We pulled |global| out of nowhere, so it's possible that it was
+      // marked gray by XPConnect. Since we're now exposing it to JS code,
+      // we need to mark it black.
+      JS::ExposeObjectToActiveJS(global);
+      if (!globals.append(global)) {
+        return false;
+      }
+    }
+  }
+
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+
+  for (size_t i = 0; i < globals.length(); i++) {
+    RootedValue globalValue(cx, ObjectValue(*globals[i]));
+    if (!dbg->wrapDebuggeeValue(cx, &globalValue)) {
+      return false;
+    }
+    if (!NewbornArrayPush(cx, result, globalValue)) {
+      return false;
+    }
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool Debugger::CallData::findSourceURLs() {
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+
+  for (WeakGlobalObjectSet::Range r = dbg->allDebuggees(); !r.empty();
+       r.popFront()) {
+    RootedObject holder(cx, r.front()->getSourceURLsHolder());
+    if (holder) {
+      for (size_t i = 0; i < holder->as<ArrayObject>().length(); i++) {
+        Value v = holder->as<ArrayObject>().getDenseElement(i);
+
+        // The value is an atom and doesn't need wrapping, but the holder may be
+        // in another zone and the atom must be marked when we create a
+        // reference in this zone.
+        MOZ_ASSERT(v.isString() && v.toString()->isAtom());
+        cx->markAtomValue(v);
+
+        if (!NewbornArrayPush(cx, result, v)) {
+          return false;
+        }
+      }
+    }
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool Debugger::CallData::makeGlobalObjectReference() {
+  if (!args.requireAtLeast(cx, "Debugger.makeGlobalObjectReference", 1)) {
+    return false;
+  }
+
+  Rooted<GlobalObject*> global(cx, dbg->unwrapDebuggeeArgument(cx, args[0]));
+  if (!global) {
+    return false;
+  }
+
+  // If we create a D.O referring to a global in an invisible realm,
+  // then from it we can reach function objects, scripts, environments, etc.,
+  // none of which we're ever supposed to see.
+  if (global->realm()->creationOptions().invisibleToDebugger()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_INVISIBLE_COMPARTMENT);
+    return false;
+  }
+
+  args.rval().setObject(*global);
+  return dbg->wrapDebuggeeValue(cx, args.rval());
+}
+
+bool Debugger::isCompilableUnit(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  if (!args.requireAtLeast(cx, "Debugger.isCompilableUnit", 1)) {
+    return false;
+  }
+
+  if (!args[0].isString()) {
+    JS_ReportErrorNumberASCII(
+        cx, GetErrorMessage, nullptr, JSMSG_NOT_EXPECTED_TYPE,
+        "Debugger.isCompilableUnit", "string", InformalValueTypeName(args[0]));
+    return false;
+  }
+
+  JSString* str = args[0].toString();
+  size_t length = str->length();
+
+  AutoStableStringChars chars(cx);
+  if (!chars.initTwoByte(cx, str)) {
+    return false;
+  }
+
+  bool result = true;
+
+  CompileOptions options(cx);
+  Rooted<frontend::CompilationStencil> stencil(
+      cx, frontend::CompilationStencil(cx, options));
+  if (!stencil.get().input.initForGlobal(cx)) {
+    return false;
+  }
+
+  LifoAllocScope allocScope(&cx->tempLifoAlloc());
+  frontend::CompilationState compilationState(cx, allocScope, options,
+                                              stencil.get());
+
+  JS::AutoSuppressWarningReporter suppressWarnings(cx);
+  frontend::Parser<frontend::FullParseHandler, char16_t> parser(
+      cx, options, chars.twoByteChars(), length,
+      /* foldConstants = */ true, stencil.get(), compilationState, nullptr,
+      nullptr);
+  if (!parser.checkOptions() || !parser.parse()) {
+    // We ran into an error. If it was because we ran out of memory we report
+    // it in the usual way.
+    if (cx->isThrowingOutOfMemory()) {
+      return false;
+    }
+
+    // If it was because we ran out of source, we return false so our caller
+    // knows to try to collect more [source].
+    if (parser.isUnexpectedEOF()) {
+      result = false;
+    }
+
+    cx->clearPendingException();
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool Debugger::CallData::adoptDebuggeeValue() {
+  if (!args.requireAtLeast(cx, "Debugger.adoptDebuggeeValue", 1)) {
+    return false;
+  }
+
+  RootedValue v(cx, args[0]);
+  if (v.isObject()) {
+    RootedObject obj(cx, &v.toObject());
+    DebuggerObject* ndobj = ToNativeDebuggerObject(cx, &obj);
+    if (!ndobj) {
+      return false;
+    }
+
+    obj.set(ndobj->referent());
+    v = ObjectValue(*obj);
+
+    if (!dbg->wrapDebuggeeValue(cx, &v)) {
+      return false;
+    }
+  }
+
+  args.rval().set(v);
+  return true;
+}
+
+class DebuggerAdoptSourceMatcher {
+  JSContext* cx_;
+  Debugger* dbg_;
+
+ public:
+  explicit DebuggerAdoptSourceMatcher(JSContext* cx, Debugger* dbg)
+      : cx_(cx), dbg_(dbg) {}
+
+  using ReturnType = DebuggerSource*;
+
+  ReturnType match(HandleScriptSourceObject source) {
+    if (source->compartment() == cx_->compartment()) {
+      JS_ReportErrorASCII(cx_,
+                          "Source is in the same compartment as this debugger");
+      return nullptr;
+    }
+    return dbg_->wrapSource(cx_, source);
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    if (wasmInstance->compartment() == cx_->compartment()) {
+      JS_ReportErrorASCII(
+          cx_, "WasmInstance is in the same compartment as this debugger");
+      return nullptr;
+    }
+    return dbg_->wrapWasmSource(cx_, wasmInstance);
+  }
+};
+
+bool Debugger::CallData::adoptFrame() {
+  if (!args.requireAtLeast(cx, "Debugger.adoptFrame", 1)) {
+    return false;
+  }
+
+  RootedObject obj(cx, RequireObject(cx, args[0]));
+  if (!obj) {
+    return false;
+  }
+
+  obj = UncheckedUnwrap(obj);
+  if (!obj->is<DebuggerFrame>()) {
+    JS_ReportErrorASCII(cx, "Argument is not a Debugger.Frame");
+    return false;
+  }
+
+  RootedValue objVal(cx, ObjectValue(*obj));
+  RootedDebuggerFrame frameObj(cx, DebuggerFrame::check(cx, objVal));
+  if (!frameObj) {
+    return false;
+  }
+
+  RootedDebuggerFrame adoptedFrame(cx);
+  if (frameObj->isOnStack()) {
+    FrameIter iter = frameObj->getFrameIter(cx);
+    if (!dbg->observesFrame(iter)) {
+      JS_ReportErrorASCII(cx, "Debugger.Frame's global is not a debuggee");
+      return false;
+    }
+    if (!dbg->getFrame(cx, iter, &adoptedFrame)) {
+      return false;
+    }
+  } else if (frameObj->isSuspended()) {
+    Rooted<AbstractGeneratorObject*> gen(cx, &frameObj->unwrappedGenerator());
+    if (!dbg->observesGlobal(&gen->global())) {
+      JS_ReportErrorASCII(cx, "Debugger.Frame's global is not a debuggee");
+      return false;
+    }
+
+    if (!dbg->getFrame(cx, gen, &adoptedFrame)) {
+      return false;
+    }
+  } else {
+    if (!dbg->getFrame(cx, &adoptedFrame)) {
+      return false;
+    }
+  }
+
+  args.rval().setObject(*adoptedFrame);
+  return true;
+}
+
+bool Debugger::CallData::adoptSource() {
+  if (!args.requireAtLeast(cx, "Debugger.adoptSource", 1)) {
+    return false;
+  }
+
+  RootedObject obj(cx, RequireObject(cx, args[0]));
+  if (!obj) {
+    return false;
+  }
+
+  obj = UncheckedUnwrap(obj);
+  if (!obj->is<DebuggerSource>()) {
+    JS_ReportErrorASCII(cx, "Argument is not a Debugger.Source");
+    return false;
+  }
+
+  RootedDebuggerSource sourceObj(cx, &obj->as<DebuggerSource>());
+  if (!sourceObj->getReferentRawObject()) {
+    JS_ReportErrorASCII(cx, "Argument is Debugger.Source.prototype");
+    return false;
+  }
+
+  Rooted<DebuggerSourceReferent> referent(cx, sourceObj->getReferent());
+
+  DebuggerAdoptSourceMatcher matcher(cx, dbg);
+  DebuggerSource* res = referent.match(matcher);
+  if (!res) {
+    return false;
+  }
+
+  args.rval().setObject(*res);
+  return true;
+}
+
+const JSPropertySpec Debugger::properties[] = {
+    JS_DEBUG_PSGS("onDebuggerStatement", getOnDebuggerStatement,
+                  setOnDebuggerStatement),
+    JS_DEBUG_PSGS("onExceptionUnwind", getOnExceptionUnwind,
+                  setOnExceptionUnwind),
+    JS_DEBUG_PSGS("onNewScript", getOnNewScript, setOnNewScript),
+    JS_DEBUG_PSGS("onNewPromise", getOnNewPromise, setOnNewPromise),
+    JS_DEBUG_PSGS("onPromiseSettled", getOnPromiseSettled, setOnPromiseSettled),
+    JS_DEBUG_PSGS("onEnterFrame", getOnEnterFrame, setOnEnterFrame),
+    JS_DEBUG_PSGS("onNativeCall", getOnNativeCall, setOnNativeCall),
+    JS_DEBUG_PSGS("onNewGlobalObject", getOnNewGlobalObject,
+                  setOnNewGlobalObject),
+    JS_DEBUG_PSGS("uncaughtExceptionHook", getUncaughtExceptionHook,
+                  setUncaughtExceptionHook),
+    JS_DEBUG_PSGS("allowUnobservedAsmJS", getAllowUnobservedAsmJS,
+                  setAllowUnobservedAsmJS),
+    JS_DEBUG_PSGS("collectCoverageInfo", getCollectCoverageInfo,
+                  setCollectCoverageInfo),
+    JS_DEBUG_PSG("memory", getMemory),
+    JS_STRING_SYM_PS(toStringTag, "Debugger", JSPROP_READONLY),
+    JS_PS_END};
+
+const JSFunctionSpec Debugger::methods[] = {
+    JS_DEBUG_FN("addDebuggee", addDebuggee, 1),
+    JS_DEBUG_FN("addAllGlobalsAsDebuggees", addAllGlobalsAsDebuggees, 0),
+    JS_DEBUG_FN("removeDebuggee", removeDebuggee, 1),
+    JS_DEBUG_FN("removeAllDebuggees", removeAllDebuggees, 0),
+    JS_DEBUG_FN("hasDebuggee", hasDebuggee, 1),
+    JS_DEBUG_FN("getDebuggees", getDebuggees, 0),
+    JS_DEBUG_FN("getNewestFrame", getNewestFrame, 0),
+    JS_DEBUG_FN("clearAllBreakpoints", clearAllBreakpoints, 0),
+    JS_DEBUG_FN("findScripts", findScripts, 1),
+    JS_DEBUG_FN("findSources", findSources, 1),
+    JS_DEBUG_FN("findObjects", findObjects, 1),
+    JS_DEBUG_FN("findAllGlobals", findAllGlobals, 0),
+    JS_DEBUG_FN("findSourceURLs", findSourceURLs, 0),
+    JS_DEBUG_FN("makeGlobalObjectReference", makeGlobalObjectReference, 1),
+    JS_DEBUG_FN("adoptDebuggeeValue", adoptDebuggeeValue, 1),
+    JS_DEBUG_FN("adoptFrame", adoptFrame, 1),
+    JS_DEBUG_FN("adoptSource", adoptSource, 1),
+    JS_FS_END};
+
+const JSFunctionSpec Debugger::static_methods[]{
+    JS_FN("isCompilableUnit", Debugger::isCompilableUnit, 1, 0), JS_FS_END};
+
+DebuggerScript* Debugger::newDebuggerScript(
+    JSContext* cx, Handle<DebuggerScriptReferent> referent) {
+  cx->check(object.get());
+
+  RootedObject proto(
+      cx, &object->getReservedSlot(JSSLOT_DEBUG_SCRIPT_PROTO).toObject());
+  MOZ_ASSERT(proto);
+  RootedNativeObject debugger(cx, object);
+
+  return DebuggerScript::create(cx, proto, referent, debugger);
+}
+
+template <typename ReferentType, typename Map>
+typename Map::WrapperType* Debugger::wrapVariantReferent(
+    JSContext* cx, Map& map,
+    Handle<typename Map::WrapperType::ReferentVariant> referent) {
+  cx->check(object);
+
+  Handle<ReferentType*> untaggedReferent =
+      referent.template as<ReferentType*>();
+  MOZ_ASSERT(cx->compartment() != untaggedReferent->compartment());
+
+  DependentAddPtr<Map> p(cx, map, untaggedReferent);
+  if (!p) {
+    typename Map::WrapperType* wrapper = newVariantWrapper(cx, referent);
+    if (!wrapper) {
+      return nullptr;
+    }
+
+    if (!p.add(cx, map, untaggedReferent, wrapper)) {
+      NukeDebuggerWrapper(wrapper);
+      return nullptr;
+    }
+  }
+
+  return &p->value()->template as<typename Map::WrapperType>();
+}
+
+DebuggerScript* Debugger::wrapVariantReferent(
+    JSContext* cx, Handle<DebuggerScriptReferent> referent) {
+  if (referent.is<BaseScript*>()) {
+    return wrapVariantReferent<BaseScript>(cx, scripts, referent);
+  }
+
+  return wrapVariantReferent<WasmInstanceObject>(cx, wasmInstanceScripts,
+                                                 referent);
+}
+
+DebuggerScript* Debugger::wrapScript(JSContext* cx,
+                                     Handle<BaseScript*> script) {
+  Rooted<DebuggerScriptReferent> referent(cx,
+                                          DebuggerScriptReferent(script.get()));
+  return wrapVariantReferent(cx, referent);
+}
+
+DebuggerScript* Debugger::wrapWasmScript(
+    JSContext* cx, Handle<WasmInstanceObject*> wasmInstance) {
+  Rooted<DebuggerScriptReferent> referent(cx, wasmInstance.get());
+  return wrapVariantReferent(cx, referent);
+}
+
+DebuggerSource* Debugger::newDebuggerSource(
+    JSContext* cx, Handle<DebuggerSourceReferent> referent) {
+  cx->check(object.get());
+
+  RootedObject proto(
+      cx, &object->getReservedSlot(JSSLOT_DEBUG_SOURCE_PROTO).toObject());
+  MOZ_ASSERT(proto);
+  RootedNativeObject debugger(cx, object);
+  return DebuggerSource::create(cx, proto, referent, debugger);
+}
+
+DebuggerSource* Debugger::wrapVariantReferent(
+    JSContext* cx, Handle<DebuggerSourceReferent> referent) {
+  DebuggerSource* obj;
+  if (referent.is<ScriptSourceObject*>()) {
+    obj = wrapVariantReferent<ScriptSourceObject>(cx, sources, referent);
+  } else {
+    obj = wrapVariantReferent<WasmInstanceObject>(cx, wasmInstanceSources,
+                                                  referent);
+  }
+  MOZ_ASSERT_IF(obj, obj->getReferent() == referent);
+  return obj;
+}
+
+DebuggerSource* Debugger::wrapSource(JSContext* cx,
+                                     HandleScriptSourceObject source) {
+  Rooted<DebuggerSourceReferent> referent(cx, source.get());
+  return wrapVariantReferent(cx, referent);
+}
+
+DebuggerSource* Debugger::wrapWasmSource(
+    JSContext* cx, Handle<WasmInstanceObject*> wasmInstance) {
+  Rooted<DebuggerSourceReferent> referent(cx, wasmInstance.get());
+  return wrapVariantReferent(cx, referent);
+}
+
+bool DebugAPI::getScriptInstrumentationId(JSContext* cx, HandleObject dbgObject,
+                                          HandleScript script,
+                                          MutableHandleValue rval) {
+  Debugger* dbg = Debugger::fromJSObject(dbgObject);
+  DebuggerScript* dbgScript = dbg->wrapScript(cx, script);
+  if (!dbgScript) {
+    return false;
+  }
+  rval.set(dbgScript->getInstrumentationId());
+  return true;
+}
+
+bool Debugger::observesFrame(AbstractFramePtr frame) const {
+  if (frame.isWasmDebugFrame()) {
+    return observesWasm(frame.wasmInstance());
+  }
+
+  return observesScript(frame.script());
+}
+
+bool Debugger::observesFrame(const FrameIter& iter) const {
+  // Skip frames not yet fully initialized during their prologue.
+  if (iter.isInterp() && iter.isFunctionFrame()) {
+    const Value& thisVal = iter.interpFrame()->thisArgument();
+    if (thisVal.isMagic() && thisVal.whyMagic() == JS_IS_CONSTRUCTING) {
+      return false;
+    }
+  }
+  if (iter.isWasm()) {
+    // Skip frame of wasm instances we cannot observe.
+    if (!iter.wasmDebugEnabled()) {
+      return false;
+    }
+    return observesWasm(iter.wasmInstance());
+  }
+  return observesScript(iter.script());
+}
+
+bool Debugger::observesScript(JSScript* script) const {
+  // Don't ever observe self-hosted scripts: the Debugger API can break
+  // self-hosted invariants.
+  return observesGlobal(&script->global()) && !script->selfHosted();
+}
+
+bool Debugger::observesWasm(wasm::Instance* instance) const {
+  if (!instance->debugEnabled()) {
+    return false;
+  }
+  return observesGlobal(&instance->object()->global());
+}
+
+/* static */
+bool Debugger::replaceFrameGuts(JSContext* cx, AbstractFramePtr from,
+                                AbstractFramePtr to, ScriptFrameIter& iter) {
+  MOZ_ASSERT(from != to);
+
+  // Rekey missingScopes to maintain Debugger.Environment identity and
+  // forward liveScopes to point to the new frame.
+  DebugEnvironments::forwardLiveFrame(cx, from, to);
+
+  // If we hit an OOM anywhere in here, we need to make sure there aren't any
+  // Debugger.Frame objects left partially-initialized.
+  auto terminateDebuggerFramesOnExit = MakeScopeExit([&] {
+    terminateDebuggerFrames(cx, from);
+    terminateDebuggerFrames(cx, to);
+
+    MOZ_ASSERT(!DebugAPI::inFrameMaps(from));
+    MOZ_ASSERT(!DebugAPI::inFrameMaps(to));
+  });
+
+  // Forward live Debugger.Frame objects.
+  Rooted<DebuggerFrameVector> frames(cx, DebuggerFrameVector(cx));
+  if (!getDebuggerFrames(from, &frames)) {
+    // An OOM here means that all Debuggers' frame maps still contain
+    // entries for 'from' and no entries for 'to'. Since the 'from' frame
+    // will be gone, they are removed by terminateDebuggerFramesOnExit
+    // above.
+    return false;
+  }
+
+  for (size_t i = 0; i < frames.length(); i++) {
+    HandleDebuggerFrame frameobj = frames[i];
+    Debugger* dbg = frameobj->owner();
+
+    // Update frame object's ScriptFrameIter::data pointer.
+    if (!frameobj->replaceFrameIterData(cx, iter)) {
+      return false;
+    }
+
+    // Add the frame object with |to| as key.
+    if (!dbg->frames.putNew(to, frameobj)) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+
+    // Remove the old frame entry after all fallible operations are completed
+    // so that an OOM will be able to clean up properly.
+    dbg->frames.remove(from);
+  }
+
+  // All frames successfuly replaced, cancel the rollback.
+  terminateDebuggerFramesOnExit.release();
+
+  MOZ_ASSERT(!DebugAPI::inFrameMaps(from));
+  MOZ_ASSERT_IF(!frames.empty(), DebugAPI::inFrameMaps(to));
+  return true;
+}
+
+/* static */
+bool DebugAPI::inFrameMaps(AbstractFramePtr frame) {
+  bool foundAny = false;
+  Debugger::forEachOnStackDebuggerFrame(
+      frame, [&](Debugger*, DebuggerFrame* frameobj) { foundAny = true; });
+  return foundAny;
+}
+
+/* static */
+void Debugger::suspendGeneratorDebuggerFrames(JSContext* cx,
+                                              AbstractFramePtr frame) {
+  JSFreeOp* fop = cx->runtime()->defaultFreeOp();
+  forEachOnStackDebuggerFrame(
+      frame, [&](Debugger* dbg, DebuggerFrame* dbgFrame) {
+        dbg->frames.remove(frame);
+
+#if DEBUG
+        MOZ_ASSERT(dbgFrame->hasGeneratorInfo());
+        AbstractGeneratorObject& genObj = dbgFrame->unwrappedGenerator();
+        GeneratorWeakMap::Ptr p = dbg->generatorFrames.lookup(&genObj);
+        MOZ_ASSERT(p);
+        MOZ_ASSERT(p->value() == dbgFrame);
+#endif
+
+        dbgFrame->suspend(fop);
+      });
+}
+
+/* static */
+void Debugger::terminateDebuggerFrames(JSContext* cx, AbstractFramePtr frame) {
+  JSFreeOp* fop = cx->runtime()->defaultFreeOp();
+
+  forEachOnStackOrSuspendedDebuggerFrame(
+      cx, frame, [&](Debugger* dbg, DebuggerFrame* dbgFrame) {
+        Debugger::terminateDebuggerFrame(fop, dbg, dbgFrame, frame);
+      });
+
+  // If this is an eval frame, then from the debugger's perspective the
+  // script is about to be destroyed. Remove any breakpoints in it.
+  if (frame.isEvalFrame()) {
+    RootedScript script(cx, frame.script());
+    DebugScript::clearBreakpointsIn(cx->runtime()->defaultFreeOp(), script,
+                                    nullptr, nullptr);
+  }
+}
+
+/* static */
+void Debugger::terminateDebuggerFrame(
+    JSFreeOp* fop, Debugger* dbg, DebuggerFrame* dbgFrame,
+    AbstractFramePtr frame, FrameMap::Enum* maybeFramesEnum,
+    GeneratorWeakMap::Enum* maybeGeneratorFramesEnum) {
+  // If we were not passed the frame, either we are destroying a frame early
+  // on before it was inserted into the "frames" list, or else we are
+  // terminating a frame from "generatorFrames" and the "frames" entries will
+  // be cleaned up later on with a second call to this function.
+  MOZ_ASSERT_IF(!frame, !maybeFramesEnum);
+  MOZ_ASSERT_IF(!frame, dbgFrame->hasGeneratorInfo());
+  MOZ_ASSERT_IF(!dbgFrame->hasGeneratorInfo(), !maybeGeneratorFramesEnum);
+
+  if (frame) {
+    if (maybeFramesEnum) {
+      maybeFramesEnum->removeFront();
+    } else {
+      dbg->frames.remove(frame);
+    }
+  }
+
+  if (dbgFrame->hasGeneratorInfo()) {
+    if (maybeGeneratorFramesEnum) {
+      maybeGeneratorFramesEnum->removeFront();
+    } else {
+      dbg->generatorFrames.remove(&dbgFrame->unwrappedGenerator());
+    }
+  }
+
+  dbgFrame->terminate(fop, frame);
+}
+
+DebuggerDebuggeeLink* Debugger::getDebuggeeLink() {
+  return &object->getReservedSlot(JSSLOT_DEBUG_DEBUGGEE_LINK)
+              .toObject()
+              .as<DebuggerDebuggeeLink>();
+}
+
+void DebuggerDebuggeeLink::setLinkSlot(Debugger& dbg) {
+  setReservedSlot(DEBUGGER_LINK_SLOT, ObjectValue(*dbg.toJSObject()));
+}
+
+void DebuggerDebuggeeLink::clearLinkSlot() {
+  setReservedSlot(DEBUGGER_LINK_SLOT, UndefinedValue());
+}
+
+const JSClass DebuggerDebuggeeLink::class_ = {
+    "DebuggerDebuggeeLink", JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS)};
+
+/* static */
+bool DebugAPI::handleBaselineOsr(JSContext* cx, InterpreterFrame* from,
+                                 jit::BaselineFrame* to) {
+  ScriptFrameIter iter(cx);
+  MOZ_ASSERT(iter.abstractFramePtr() == to);
+  return Debugger::replaceFrameGuts(cx, from, to, iter);
+}
+
+/* static */
+bool DebugAPI::handleIonBailout(JSContext* cx, jit::RematerializedFrame* from,
+                                jit::BaselineFrame* to) {
+  // When we return to a bailed-out Ion real frame, we must update all
+  // Debugger.Frames that refer to its inline frames. However, since we
+  // can't pop individual inline frames off the stack (we can only pop the
+  // real frame that contains them all, as a unit), we cannot assume that
+  // the frame we're dealing with is the top frame. Advance the iterator
+  // across any inlined frames younger than |to|, the baseline frame
+  // reconstructed during bailout from the Ion frame corresponding to
+  // |from|.
+  ScriptFrameIter iter(cx);
+  while (iter.abstractFramePtr() != to) {
+    ++iter;
+  }
+  return Debugger::replaceFrameGuts(cx, from, to, iter);
+}
+
+/* static */
+void DebugAPI::handleUnrecoverableIonBailoutError(
+    JSContext* cx, jit::RematerializedFrame* frame) {
+  // Ion bailout can fail due to overrecursion. In such cases we cannot
+  // honor any further Debugger hooks on the frame, and need to ensure that
+  // its Debugger.Frame entry is cleaned up.
+  Debugger::terminateDebuggerFrames(cx, frame);
+}
+
+/*** JS::dbg::Builder *******************************************************/
+
+Builder::Builder(JSContext* cx, js::Debugger* debugger)
+    : debuggerObject(cx, debugger->toJSObject().get()), debugger(debugger) {}
+
+#if DEBUG
+void Builder::assertBuilt(JSObject* obj) {
+  // We can't use assertSameCompartment here, because that is always keyed to
+  // some JSContext's current compartment, whereas BuiltThings can be
+  // constructed and assigned to without respect to any particular context;
+  // the only constraint is that they should be in their debugger's compartment.
+  MOZ_ASSERT_IF(obj, debuggerObject->compartment() == obj->compartment());
+}
+#endif
+
+bool Builder::Object::definePropertyToTrusted(JSContext* cx, const char* name,
+                                              JS::MutableHandleValue trusted) {
+  // We should have checked for false Objects before calling this.
+  MOZ_ASSERT(value);
+
+  JSAtom* atom = Atomize(cx, name, strlen(name));
+  if (!atom) {
+    return false;
+  }
+  RootedId id(cx, AtomToId(atom));
+
+  return DefineDataProperty(cx, value, id, trusted);
+}
+
+bool Builder::Object::defineProperty(JSContext* cx, const char* name,
+                                     JS::HandleValue propval_) {
+  AutoRealm ar(cx, debuggerObject());
+
+  RootedValue propval(cx, propval_);
+  if (!debugger()->wrapDebuggeeValue(cx, &propval)) {
+    return false;
+  }
+
+  return definePropertyToTrusted(cx, name, &propval);
+}
+
+bool Builder::Object::defineProperty(JSContext* cx, const char* name,
+                                     JS::HandleObject propval_) {
+  RootedValue propval(cx, ObjectOrNullValue(propval_));
+  return defineProperty(cx, name, propval);
+}
+
+bool Builder::Object::defineProperty(JSContext* cx, const char* name,
+                                     Builder::Object& propval_) {
+  AutoRealm ar(cx, debuggerObject());
+
+  RootedValue propval(cx, ObjectOrNullValue(propval_.value));
+  return definePropertyToTrusted(cx, name, &propval);
+}
+
+Builder::Object Builder::newObject(JSContext* cx) {
+  AutoRealm ar(cx, debuggerObject);
+
+  RootedPlainObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx));
+
+  // If the allocation failed, this will return a false Object, as the spec
+  // promises.
+  return Object(cx, *this, obj);
+}
+
+/*** JS::dbg::AutoEntryMonitor **********************************************/
+
+AutoEntryMonitor::AutoEntryMonitor(JSContext* cx)
+    : cx_(cx), savedMonitor_(cx->entryMonitor) {
+  cx->entryMonitor = this;
+}
+
+AutoEntryMonitor::~AutoEntryMonitor() { cx_->entryMonitor = savedMonitor_; }
+
+/*** Glue *******************************************************************/
+
+extern JS_PUBLIC_API bool JS_DefineDebuggerObject(JSContext* cx,
+                                                  HandleObject obj) {
+  RootedNativeObject debugCtor(cx), debugProto(cx), frameProto(cx),
+      scriptProto(cx), sourceProto(cx), objectProto(cx), envProto(cx),
+      memoryProto(cx);
+  RootedObject debuggeeWouldRunProto(cx);
+  RootedValue debuggeeWouldRunCtor(cx);
+  Handle<GlobalObject*> global = obj.as<GlobalObject>();
+
+  debugProto =
+      InitClass(cx, global, nullptr, &DebuggerInstanceObject::class_,
+                Debugger::construct, 1, Debugger::properties, Debugger::methods,
+                nullptr, Debugger::static_methods, debugCtor.address());
+  if (!debugProto) {
+    return false;
+  }
+
+  frameProto = DebuggerFrame::initClass(cx, global, debugCtor);
+  if (!frameProto) {
+    return false;
+  }
+
+  scriptProto = DebuggerScript::initClass(cx, global, debugCtor);
+  if (!scriptProto) {
+    return false;
+  }
+
+  sourceProto = DebuggerSource::initClass(cx, global, debugCtor);
+  if (!sourceProto) {
+    return false;
+  }
+
+  objectProto = DebuggerObject::initClass(cx, global, debugCtor);
+  if (!objectProto) {
+    return false;
+  }
+
+  envProto = DebuggerEnvironment::initClass(cx, global, debugCtor);
+  if (!envProto) {
+    return false;
+  }
+
+  memoryProto =
+      InitClass(cx, debugCtor, nullptr, &DebuggerMemory::class_,
+                DebuggerMemory::construct, 0, DebuggerMemory::properties,
+                DebuggerMemory::methods, nullptr, nullptr);
+  if (!memoryProto) {
+    return false;
+  }
+
+  debuggeeWouldRunProto = GlobalObject::getOrCreateCustomErrorPrototype(
+      cx, global, JSEXN_DEBUGGEEWOULDRUN);
+  if (!debuggeeWouldRunProto) {
+    return false;
+  }
+  debuggeeWouldRunCtor = global->getConstructor(JSProto_DebuggeeWouldRun);
+  RootedId debuggeeWouldRunId(
+      cx, NameToId(ClassName(JSProto_DebuggeeWouldRun, cx)));
+  if (!DefineDataProperty(cx, debugCtor, debuggeeWouldRunId,
+                          debuggeeWouldRunCtor, 0)) {
+    return false;
+  }
+
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_FRAME_PROTO,
+                              ObjectValue(*frameProto));
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_OBJECT_PROTO,
+                              ObjectValue(*objectProto));
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_SCRIPT_PROTO,
+                              ObjectValue(*scriptProto));
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_SOURCE_PROTO,
+                              ObjectValue(*sourceProto));
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_ENV_PROTO,
+                              ObjectValue(*envProto));
+  debugProto->setReservedSlot(Debugger::JSSLOT_DEBUG_MEMORY_PROTO,
+                              ObjectValue(*memoryProto));
+  return true;
+}
+
+JS_PUBLIC_API bool JS::dbg::IsDebugger(JSObject& obj) {
+  /* We only care about debugger objects, so CheckedUnwrapStatic is OK. */
+  JSObject* unwrapped = CheckedUnwrapStatic(&obj);
+  return unwrapped && unwrapped->is<DebuggerInstanceObject>() &&
+         js::Debugger::fromJSObject(unwrapped) != nullptr;
+}
+
+JS_PUBLIC_API bool JS::dbg::GetDebuggeeGlobals(
+    JSContext* cx, JSObject& dbgObj, MutableHandleObjectVector vector) {
+  MOZ_ASSERT(IsDebugger(dbgObj));
+  /* Since we know we have a debugger object, CheckedUnwrapStatic is fine. */
+  js::Debugger* dbg = js::Debugger::fromJSObject(CheckedUnwrapStatic(&dbgObj));
+
+  if (!vector.reserve(vector.length() + dbg->debuggees.count())) {
+    JS_ReportOutOfMemory(cx);
+    return false;
+  }
+
+  for (WeakGlobalObjectSet::Range r = dbg->allDebuggees(); !r.empty();
+       r.popFront()) {
+    vector.infallibleAppend(static_cast<JSObject*>(r.front()));
+  }
+
+  return true;
+}
+
+#ifdef DEBUG
+/* static */
+bool Debugger::isDebuggerCrossCompartmentEdge(JSObject* obj,
+                                              const gc::Cell* target) {
+  MOZ_ASSERT(target);
+
+  const gc::Cell* referent = nullptr;
+  if (obj->is<DebuggerScript>()) {
+    referent = obj->as<DebuggerScript>().getReferentCell();
+  } else if (obj->is<DebuggerSource>()) {
+    referent = obj->as<DebuggerSource>().getReferentRawObject();
+  } else if (obj->is<DebuggerObject>()) {
+    referent = obj->as<DebuggerObject>().referent();
+  } else if (obj->is<DebuggerEnvironment>()) {
+    referent = obj->as<DebuggerEnvironment>().referent();
+  }
+
+  return referent == target;
+}
+
+static void CheckDebuggeeThingRealm(Realm* realm, bool invisibleOk) {
+  MOZ_ASSERT(!realm->creationOptions().mergeable());
+  MOZ_ASSERT_IF(!invisibleOk, !realm->creationOptions().invisibleToDebugger());
+}
+
+void js::CheckDebuggeeThing(BaseScript* script, bool invisibleOk) {
+  CheckDebuggeeThingRealm(script->realm(), invisibleOk);
+}
+
+void js::CheckDebuggeeThing(JSObject* obj, bool invisibleOk) {
+  if (Realm* realm = JS::GetObjectRealmOrNull(obj)) {
+    CheckDebuggeeThingRealm(realm, invisibleOk);
+  }
+}
+#endif  // DEBUG
+
+/*** JS::dbg::GarbageCollectionEvent ****************************************/
+
+namespace JS {
+namespace dbg {
+
+/* static */ GarbageCollectionEvent::Ptr GarbageCollectionEvent::Create(
+    JSRuntime* rt, ::js::gcstats::Statistics& stats, uint64_t gcNumber) {
+  auto data = MakeUnique<GarbageCollectionEvent>(gcNumber);
+  if (!data) {
+    return nullptr;
+  }
+
+  data->nonincrementalReason = stats.nonincrementalReason();
+
+  for (auto& slice : stats.slices()) {
+    if (!data->reason) {
+      // There is only one GC reason for the whole cycle, but for legacy
+      // reasons this data is stored and replicated on each slice. Each
+      // slice used to have its own GCReason, but now they are all the
+      // same.
+      data->reason = ExplainGCReason(slice.reason);
+      MOZ_ASSERT(data->reason);
+    }
+
+    if (!data->collections.growBy(1)) {
+      return nullptr;
+    }
+
+    data->collections.back().startTimestamp = slice.start;
+    data->collections.back().endTimestamp = slice.end;
+  }
+
+  return data;
+}
+
+static bool DefineStringProperty(JSContext* cx, HandleObject obj,
+                                 PropertyName* propName, const char* strVal) {
+  RootedValue val(cx, UndefinedValue());
+  if (strVal) {
+    JSAtom* atomized = Atomize(cx, strVal, strlen(strVal));
+    if (!atomized) {
+      return false;
+    }
+    val = StringValue(atomized);
+  }
+  return DefineDataProperty(cx, obj, propName, val);
+}
+
+JSObject* GarbageCollectionEvent::toJSObject(JSContext* cx) const {
+  RootedObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx));
+  RootedValue gcCycleNumberVal(cx, NumberValue(majorGCNumber_));
+  if (!obj ||
+      !DefineStringProperty(cx, obj, cx->names().nonincrementalReason,
+                            nonincrementalReason) ||
+      !DefineStringProperty(cx, obj, cx->names().reason, reason) ||
+      !DefineDataProperty(cx, obj, cx->names().gcCycleNumber,
+                          gcCycleNumberVal)) {
+    return nullptr;
+  }
+
+  RootedArrayObject slicesArray(cx, NewDenseEmptyArray(cx));
+  if (!slicesArray) {
+    return nullptr;
+  }
+
+  TimeStamp originTime = TimeStamp::ProcessCreation();
+
+  size_t idx = 0;
+  for (auto range = collections.all(); !range.empty(); range.popFront()) {
+    RootedPlainObject collectionObj(cx,
+                                    NewBuiltinClassInstance<PlainObject>(cx));
+    if (!collectionObj) {
+      return nullptr;
+    }
+
+    RootedValue start(cx), end(cx);
+    start = NumberValue(
+        (range.front().startTimestamp - originTime).ToMilliseconds());
+    end =
+        NumberValue((range.front().endTimestamp - originTime).ToMilliseconds());
+    if (!DefineDataProperty(cx, collectionObj, cx->names().startTimestamp,
+                            start) ||
+        !DefineDataProperty(cx, collectionObj, cx->names().endTimestamp, end)) {
+      return nullptr;
+    }
+
+    RootedValue collectionVal(cx, ObjectValue(*collectionObj));
+    if (!DefineDataElement(cx, slicesArray, idx++, collectionVal)) {
+      return nullptr;
+    }
+  }
+
+  RootedValue slicesValue(cx, ObjectValue(*slicesArray));
+  if (!DefineDataProperty(cx, obj, cx->names().collections, slicesValue)) {
+    return nullptr;
+  }
+
+  return obj;
+}
+
+JS_PUBLIC_API bool FireOnGarbageCollectionHookRequired(JSContext* cx) {
+  AutoCheckCannotGC noGC;
+
+  for (auto& dbg : cx->runtime()->onGarbageCollectionWatchers()) {
+    MOZ_ASSERT(dbg.getHook(Debugger::OnGarbageCollection));
+    if (dbg.observedGC(cx->runtime()->gc.majorGCCount())) {
+      return true;
+    }
+  }
+
+  return false;
+}
+
+JS_PUBLIC_API bool FireOnGarbageCollectionHook(
+    JSContext* cx, JS::dbg::GarbageCollectionEvent::Ptr&& data) {
+  RootedObjectVector triggered(cx);
+
+  {
+    // We had better not GC (and potentially get a dangling Debugger
+    // pointer) while finding all Debuggers observing a debuggee that
+    // participated in this GC.
+    AutoCheckCannotGC noGC;
+
+    for (auto& dbg : cx->runtime()->onGarbageCollectionWatchers()) {
+      MOZ_ASSERT(dbg.getHook(Debugger::OnGarbageCollection));
+      if (dbg.observedGC(data->majorGCNumber())) {
+        if (!triggered.append(dbg.object)) {
+          JS_ReportOutOfMemory(cx);
+          return false;
+        }
+      }
+    }
+  }
+
+  for (; !triggered.empty(); triggered.popBack()) {
+    Debugger* dbg = Debugger::fromJSObject(triggered.back());
+
+    if (dbg->getHook(Debugger::OnGarbageCollection)) {
+      mozilla::Unused << dbg->enterDebuggerHook(cx, [&]() -> bool {
+        return dbg->fireOnGarbageCollectionHook(cx, data);
+      });
+      MOZ_ASSERT(!cx->isExceptionPending());
+    }
+  }
+
+  return true;
+}
+
+}  // namespace dbg
+}  // namespace JS
diff --git a/js/src/debugger/Debugger.h b/js/src/debugger/Debugger.h
new file mode 100644
index 0000000000..8dccbfddbe
--- /dev/null
+++ b/js/src/debugger/Debugger.h
@@ -0,0 +1,1617 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Debugger_h
+#define debugger_Debugger_h
+
+#include "mozilla/Assertions.h"        // for MOZ_ASSERT_HELPER1
+#include "mozilla/Attributes.h"        // for MOZ_MUST_USE, MOZ_RAII
+#include "mozilla/DoublyLinkedList.h"  // for DoublyLinkedListElement
+#include "mozilla/HashTable.h"         // for HashSet, DefaultHasher (ptr only)
+#include "mozilla/LinkedList.h"        // for LinkedList (ptr only)
+#include "mozilla/Maybe.h"             // for Maybe, Nothing
+#include "mozilla/Range.h"             // for Range
+#include "mozilla/Result.h"            // for Result
+#include "mozilla/TimeStamp.h"         // for TimeStamp
+#include "mozilla/Variant.h"           // for Variant
+
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for uint32_t, uint64_t, uintptr_t
+#include <utility>   // for std::move
+
+#include "jsapi.h"             // for Handle, UnsafeTraceRoot
+#include "jstypes.h"           // for JS_GC_ZEAL
+#include "NamespaceImports.h"  // for Value, HandleObject
+
+#include "debugger/DebugAPI.h"      // for DebugAPI
+#include "debugger/Object.h"        // for DebuggerObject
+#include "ds/TraceableFifo.h"       // for TraceableFifo
+#include "gc/Barrier.h"             // for WeakHeapPtrGlobalObject, HeapPtr
+#include "gc/Marking.h"             // for IsAboutToBeFinalized, ToMarkable
+#include "gc/Rooting.h"             // for HandleSavedFrame, HandleAtom
+#include "gc/Tracer.h"              // for TraceNullableEdge, TraceEdge
+#include "gc/WeakMap.h"             // for WeakMap
+#include "gc/ZoneAllocator.h"       // for ZoneAllocPolicy
+#include "js/GCAPI.h"               // for GarbageCollectionEvent
+#include "js/Proxy.h"               // for PropertyDescriptor
+#include "js/Wrapper.h"             // for UncheckedUnwrap
+#include "proxy/DeadObjectProxy.h"  // for IsDeadProxyObject
+#include "vm/GeneratorObject.h"     // for AbstractGeneratorObject
+#include "vm/GlobalObject.h"        // for GlobalObject
+#include "vm/JSContext.h"           // for JSContext
+#include "vm/JSObject.h"            // for JSObject
+#include "vm/JSScript.h"            // for JSScript, ScriptSourceObject
+#include "vm/NativeObject.h"        // for NativeObject
+#include "vm/Runtime.h"             // for JSRuntime
+#include "vm/SavedFrame.h"          // for SavedFrame
+#include "vm/Stack.h"               // for AbstractFramePtr, FrameIter
+#include "vm/StringType.h"          // for JSAtom
+#include "wasm/WasmJS.h"            // for WasmInstanceObject
+
+class JS_PUBLIC_API JSFunction;
+
+namespace JS {
+class JS_FRIEND_API AutoStableStringChars;
+class JS_PUBLIC_API Compartment;
+class JS_PUBLIC_API Realm;
+class JS_PUBLIC_API Zone;
+} /* namespace JS */
+
+namespace js {
+class AutoRealm;
+class CrossCompartmentKey;
+class Debugger;
+class DebuggerEnvironment;
+class PromiseObject;
+namespace gc {
+struct Cell;
+} /* namespace gc */
+namespace wasm {
+class Instance;
+} /* namespace wasm */
+} /* namespace js */
+
+/*
+ * Windows 3.x used a cooperative multitasking model, with a Yield macro that
+ * let you relinquish control to other cooperative threads. Microsoft replaced
+ * it with an empty macro long ago. We should be free to use it in our code.
+ */
+#undef Yield
+
+namespace js {
+
+class Breakpoint;
+class DebuggerFrame;
+class DebuggerScript;
+class DebuggerSource;
+class DebuggerMemory;
+class ScriptedOnStepHandler;
+class ScriptedOnPopHandler;
+class DebuggerDebuggeeLink;
+
+/**
+ * Tells how the JS engine should resume debuggee execution after firing a
+ * debugger hook.  Most debugger hooks get to choose how the debuggee proceeds;
+ * see js/src/doc/Debugger/Conventions.md under "Resumption Values".
+ *
+ * Debugger::processHandlerResult() translates between JavaScript values and
+ * this enum.
+ */
+enum class ResumeMode {
+  /**
+   * The debuggee should continue unchanged.
+   *
+   * This corresponds to a resumption value of `undefined`.
+   */
+  Continue,
+
+  /**
+   * Throw an exception in the debuggee.
+   *
+   * This corresponds to a resumption value of `{throw: <value>}`.
+   */
+  Throw,
+
+  /**
+   * Terminate the debuggee, as if it had been cancelled via the "slow
+   * script" ribbon.
+   *
+   * This corresponds to a resumption value of `null`.
+   */
+  Terminate,
+
+  /**
+   * Force the debuggee to return from the current frame.
+   *
+   * This corresponds to a resumption value of `{return: <value>}`.
+   */
+  Return,
+};
+
+/**
+ * A completion value, describing how some sort of JavaScript evaluation
+ * completed. This is used to tell an onPop handler what's going on with the
+ * frame, and to report the outcome of call, apply, setProperty, and getProperty
+ * operations.
+ *
+ * Local variables of type Completion should be held in Rooted locations,
+ * and passed using Handle and MutableHandle.
+ */
+class Completion {
+ public:
+  struct Return {
+    explicit Return(const Value& value) : value(value) {}
+    Value value;
+
+    void trace(JSTracer* trc) {
+      JS::UnsafeTraceRoot(trc, &value, "js::Completion::Return::value");
+    }
+  };
+
+  struct Throw {
+    Throw(const Value& exception, SavedFrame* stack)
+        : exception(exception), stack(stack) {}
+    Value exception;
+    SavedFrame* stack;
+
+    void trace(JSTracer* trc) {
+      JS::UnsafeTraceRoot(trc, &exception, "js::Completion::Throw::exception");
+      JS::UnsafeTraceRoot(trc, &stack, "js::Completion::Throw::stack");
+    }
+  };
+
+  struct Terminate {
+    void trace(JSTracer* trc) {}
+  };
+
+  struct InitialYield {
+    explicit InitialYield(AbstractGeneratorObject* generatorObject)
+        : generatorObject(generatorObject) {}
+    AbstractGeneratorObject* generatorObject;
+
+    void trace(JSTracer* trc) {
+      JS::UnsafeTraceRoot(trc, &generatorObject,
+                          "js::Completion::InitialYield::generatorObject");
+    }
+  };
+
+  struct Yield {
+    Yield(AbstractGeneratorObject* generatorObject, const Value& iteratorResult)
+        : generatorObject(generatorObject), iteratorResult(iteratorResult) {}
+    AbstractGeneratorObject* generatorObject;
+    Value iteratorResult;
+
+    void trace(JSTracer* trc) {
+      JS::UnsafeTraceRoot(trc, &generatorObject,
+                          "js::Completion::Yield::generatorObject");
+      JS::UnsafeTraceRoot(trc, &iteratorResult,
+                          "js::Completion::Yield::iteratorResult");
+    }
+  };
+
+  struct Await {
+    Await(AbstractGeneratorObject* generatorObject, const Value& awaitee)
+        : generatorObject(generatorObject), awaitee(awaitee) {}
+    AbstractGeneratorObject* generatorObject;
+    Value awaitee;
+
+    void trace(JSTracer* trc) {
+      JS::UnsafeTraceRoot(trc, &generatorObject,
+                          "js::Completion::Await::generatorObject");
+      JS::UnsafeTraceRoot(trc, &awaitee, "js::Completion::Await::awaitee");
+    }
+  };
+
+  // The JS::Result macros want to assign to an existing variable, so having a
+  // default constructor is handy.
+  Completion() : variant(Terminate()) {}
+
+  // Construct a completion from a specific variant.
+  //
+  // Unfortunately, using a template here would prevent the implicit definitions
+  // of the copy and move constructor and assignment operators, which is icky.
+  explicit Completion(Return&& variant)
+      : variant(std::forward<Return>(variant)) {}
+  explicit Completion(Throw&& variant)
+      : variant(std::forward<Throw>(variant)) {}
+  explicit Completion(Terminate&& variant)
+      : variant(std::forward<Terminate>(variant)) {}
+  explicit Completion(InitialYield&& variant)
+      : variant(std::forward<InitialYield>(variant)) {}
+  explicit Completion(Yield&& variant)
+      : variant(std::forward<Yield>(variant)) {}
+  explicit Completion(Await&& variant)
+      : variant(std::forward<Await>(variant)) {}
+
+  // Capture a JavaScript operation result as a Completion value. This clears
+  // any exception and stack from cx, taking ownership of them itself.
+  static Completion fromJSResult(JSContext* cx, bool ok, const Value& rv);
+
+  // Construct a completion given an AbstractFramePtr that is being popped. This
+  // clears any exception and stack from cx, taking ownership of them itself.
+  static Completion fromJSFramePop(JSContext* cx, AbstractFramePtr frame,
+                                   const jsbytecode* pc, bool ok);
+
+  template <typename V>
+  bool is() const {
+    return variant.template is<V>();
+  }
+
+  template <typename V>
+  V& as() {
+    return variant.template as<V>();
+  }
+
+  template <typename V>
+  const V& as() const {
+    return variant.template as<V>();
+  }
+
+  void trace(JSTracer* trc);
+
+  /* True if this completion is a suspension of a generator or async call. */
+  bool suspending() const {
+    return variant.is<InitialYield>() || variant.is<Yield>() ||
+           variant.is<Await>();
+  }
+
+  /* Set `result` to a Debugger API completion value describing this completion.
+   */
+  bool buildCompletionValue(JSContext* cx, Debugger* dbg,
+                            MutableHandleValue result) const;
+
+  /*
+   * Set `resumeMode`, `value`, and `exnStack` to values describing this
+   * completion.
+   */
+  void toResumeMode(ResumeMode& resumeMode, MutableHandleValue value,
+                    MutableHandleSavedFrame exnStack) const;
+  /*
+   * Given a `ResumeMode` and value (typically derived from a resumption value
+   * returned by a Debugger hook), update this completion as requested.
+   */
+  void updateFromHookResult(ResumeMode resumeMode, HandleValue value);
+
+ private:
+  using Variant =
+      mozilla::Variant<Return, Throw, Terminate, InitialYield, Yield, Await>;
+  struct BuildValueMatcher;
+  struct ToResumeModeMatcher;
+
+  Variant variant;
+};
+
+typedef HashSet<WeakHeapPtrGlobalObject,
+                MovableCellHasher<WeakHeapPtrGlobalObject>, ZoneAllocPolicy>
+    WeakGlobalObjectSet;
+
+#ifdef DEBUG
+extern void CheckDebuggeeThing(BaseScript* script, bool invisibleOk);
+
+extern void CheckDebuggeeThing(JSObject* obj, bool invisibleOk);
+#endif
+
+/*
+ * [SMDOC] Cross-compartment weakmap entries for Debugger API objects
+ *
+ * The Debugger API creates objects like Debugger.Object, Debugger.Script,
+ * Debugger.Environment, etc. to refer to things in the debuggee. Each Debugger
+ * gets at most one Debugger.Mumble for each referent: Debugger.Mumbles are
+ * unique per referent per Debugger. This is accomplished by storing the
+ * debugger objects in a DebuggerWeakMap, using the debuggee thing as the key.
+ *
+ * Since a Debugger and its debuggee must be in different compartments, a
+ * Debugger.Mumble's pointer to its referent is a cross-compartment edge, from
+ * the debugger's compartment into the debuggee compartment. Like any other sort
+ * of cross-compartment edge, the GC needs to be able to find all of these edges
+ * readily. The GC therefore consults the debugger's weakmap tables as
+ * necessary.  This allows the garbage collector to easily find edges between
+ * debuggee object compartments and debugger compartments when calculating the
+ * zone sweep groups.
+ *
+ * The current implementation results in all debuggee object compartments being
+ * swept in the same group as the debugger. This is a conservative approach, and
+ * compartments may be unnecessarily grouped. However this results in a simpler
+ * and faster implementation.
+ */
+
+/*
+ * A weakmap from GC thing keys to JSObject values that supports the keys being
+ * in different compartments to the values. All values must be in the same
+ * compartment.
+ *
+ * If InvisibleKeysOk is true, then the map can have keys in invisible-to-
+ * debugger compartments. If it is false, we assert that such entries are never
+ * created.
+ *
+ * Note that keys in these weakmaps can be in any compartment, debuggee or not,
+ * because they are not deleted when a compartment is no longer a debuggee: the
+ * values need to maintain object identity across add/remove/add
+ * transitions. (Frames are an exception to the rule. Existing Debugger.Frame
+ * objects are killed if their realm is removed as a debugger; if the realm
+ * beacomes a debuggee again later, new Frame objects are created.)
+ */
+template <class Referent, class Wrapper, bool InvisibleKeysOk = false>
+class DebuggerWeakMap : private WeakMap<HeapPtr<Referent*>, HeapPtr<Wrapper*>> {
+ private:
+  using Key = HeapPtr<Referent*>;
+  using Value = HeapPtr<Wrapper*>;
+
+  JS::Compartment* compartment;
+
+ public:
+  typedef WeakMap<Key, Value> Base;
+  using ReferentType = Referent;
+  using WrapperType = Wrapper;
+
+  explicit DebuggerWeakMap(JSContext* cx)
+      : Base(cx), compartment(cx->compartment()) {}
+
+ public:
+  // Expose those parts of HashMap public interface that are used by Debugger
+  // methods.
+
+  using Entry = typename Base::Entry;
+  using Ptr = typename Base::Ptr;
+  using AddPtr = typename Base::AddPtr;
+  using Range = typename Base::Range;
+  using Lookup = typename Base::Lookup;
+
+  // Expose WeakMap public interface.
+
+  using Base::all;
+  using Base::has;
+  using Base::lookup;
+  using Base::lookupForAdd;
+  using Base::lookupUnbarriered;
+  using Base::remove;
+  using Base::trace;
+  using Base::zone;
+#ifdef DEBUG
+  using Base::hasEntry;
+#endif
+
+  class Enum : public Base::Enum {
+   public:
+    explicit Enum(DebuggerWeakMap& map) : Base::Enum(map) {}
+  };
+
+  template <typename KeyInput, typename ValueInput>
+  bool relookupOrAdd(AddPtr& p, const KeyInput& k, const ValueInput& v) {
+    MOZ_ASSERT(v->compartment() == this->compartment);
+#ifdef DEBUG
+    CheckDebuggeeThing(k, InvisibleKeysOk);
+#endif
+    MOZ_ASSERT(!Base::has(k));
+    bool ok = Base::relookupOrAdd(p, k, v);
+    return ok;
+  }
+
+ public:
+  void traceCrossCompartmentEdges(JSTracer* tracer) {
+    for (Enum e(*this); !e.empty(); e.popFront()) {
+      TraceEdge(tracer, &e.front().mutableKey(), "Debugger WeakMap key");
+      e.front().value()->trace(tracer);
+    }
+  }
+
+  bool findSweepGroupEdges() override;
+
+ private:
+#ifdef JS_GC_ZEAL
+  // Let the weak map marking verifier know that this map can
+  // contain keys in other zones.
+  virtual bool allowKeysInOtherZones() const override { return true; }
+#endif
+};
+
+class LeaveDebuggeeNoExecute;
+
+class MOZ_RAII EvalOptions {
+  JS::UniqueChars filename_;
+  unsigned lineno_ = 1;
+
+ public:
+  EvalOptions() = default;
+  ~EvalOptions() = default;
+  const char* filename() const { return filename_.get(); }
+  unsigned lineno() const { return lineno_; }
+  MOZ_MUST_USE bool setFilename(JSContext* cx, const char* filename);
+  void setLineno(unsigned lineno) { lineno_ = lineno; }
+};
+
+/*
+ * Env is the type of what ES5 calls "lexical environments" (runtime activations
+ * of lexical scopes). This is currently just JSObject, and is implemented by
+ * CallObject, LexicalEnvironmentObject, and WithEnvironmentObject, among
+ * others--but environments and objects are really two different concepts.
+ */
+using Env = JSObject;
+
+// The referent of a Debugger.Script.
+//
+// - For most scripts, we point at their BaseScript.
+//
+// - For Web Assembly instances for which we are presenting a script-like
+//   interface, we point at their WasmInstanceObject.
+//
+// The DebuggerScript object itself simply stores a Cell* in its private
+// pointer, but when we're working with that pointer in C++ code, we'd rather
+// not pass around a Cell* and be constantly asserting that, yes, this really
+// does point to something okay. Instead, we immediately build an instance of
+// this type from the Cell* and use that instead, so we can benefit from
+// Variant's static checks.
+typedef mozilla::Variant<BaseScript*, WasmInstanceObject*>
+    DebuggerScriptReferent;
+
+// The referent of a Debugger.Source.
+//
+// - For most sources, this is a ScriptSourceObject.
+//
+// - For Web Assembly instances for which we are presenting a source-like
+//   interface, we point at their WasmInstanceObject.
+//
+// The DebuggerSource object actually simply stores a Cell* in its private
+// pointer. See the comments for DebuggerScriptReferent for the rationale for
+// this type.
+typedef mozilla::Variant<ScriptSourceObject*, WasmInstanceObject*>
+    DebuggerSourceReferent;
+
+template <typename HookIsEnabledFun /* bool (Debugger*) */>
+class MOZ_RAII DebuggerList {
+ private:
+  // Note: In the general case, 'debuggers' contains references to objects in
+  // different compartments--every compartment *except* the debugger's.
+  RootedValueVector debuggers;
+  HookIsEnabledFun hookIsEnabled;
+
+ public:
+  /**
+   * The hook function will be called during `init()` to build the list of
+   * active debuggers, and again during dispatch to validate that the hook is
+   * still active for the given debugger.
+   */
+  DebuggerList(JSContext* cx, HookIsEnabledFun hookIsEnabled)
+      : debuggers(cx), hookIsEnabled(hookIsEnabled) {}
+
+  MOZ_MUST_USE bool init(JSContext* cx);
+
+  bool empty() { return debuggers.empty(); }
+
+  template <typename FireHookFun /* ResumeMode (Debugger*) */>
+  bool dispatchHook(JSContext* cx, FireHookFun fireHook);
+
+  template <typename FireHookFun /* void (Debugger*) */>
+  void dispatchQuietHook(JSContext* cx, FireHookFun fireHook);
+
+  template <typename FireHookFun /* bool (Debugger*, ResumeMode&, MutableHandleValue) */>
+  MOZ_MUST_USE bool dispatchResumptionHook(JSContext* cx,
+                                           AbstractFramePtr frame,
+                                           FireHookFun fireHook);
+};
+
+class DebuggerInstanceObject : public NativeObject {
+ private:
+  static const JSClassOps classOps_;
+
+ public:
+  static const JSClass class_;
+};
+
+class Debugger : private mozilla::LinkedListElement<Debugger> {
+  friend class DebugAPI;
+  friend class Breakpoint;
+  friend class DebuggerFrame;
+  friend class DebuggerMemory;
+  friend class DebuggerInstanceObject;
+
+  template <typename>
+  friend class DebuggerList;
+  friend struct JSRuntime::GlobalObjectWatchersLinkAccess<Debugger>;
+  friend struct JSRuntime::GarbageCollectionWatchersLinkAccess<Debugger>;
+  friend class SavedStacks;
+  friend class ScriptedOnStepHandler;
+  friend class ScriptedOnPopHandler;
+  friend class mozilla::LinkedListElement<Debugger>;
+  friend class mozilla::LinkedList<Debugger>;
+  friend bool(::JS_DefineDebuggerObject)(JSContext* cx, JS::HandleObject obj);
+  friend bool(::JS::dbg::IsDebugger)(JSObject&);
+  friend bool(::JS::dbg::GetDebuggeeGlobals)(JSContext*, JSObject&,
+                                             MutableHandleObjectVector);
+  friend bool JS::dbg::FireOnGarbageCollectionHookRequired(JSContext* cx);
+  friend bool JS::dbg::FireOnGarbageCollectionHook(
+      JSContext* cx, JS::dbg::GarbageCollectionEvent::Ptr&& data);
+
+ public:
+  enum Hook {
+    OnDebuggerStatement,
+    OnExceptionUnwind,
+    OnNewScript,
+    OnEnterFrame,
+    OnNativeCall,
+    OnNewGlobalObject,
+    OnNewPromise,
+    OnPromiseSettled,
+    OnGarbageCollection,
+    HookCount
+  };
+  enum {
+    JSSLOT_DEBUG_PROTO_START,
+    JSSLOT_DEBUG_FRAME_PROTO = JSSLOT_DEBUG_PROTO_START,
+    JSSLOT_DEBUG_ENV_PROTO,
+    JSSLOT_DEBUG_OBJECT_PROTO,
+    JSSLOT_DEBUG_SCRIPT_PROTO,
+    JSSLOT_DEBUG_SOURCE_PROTO,
+    JSSLOT_DEBUG_MEMORY_PROTO,
+    JSSLOT_DEBUG_PROTO_STOP,
+    JSSLOT_DEBUG_HOOK_START = JSSLOT_DEBUG_PROTO_STOP,
+    JSSLOT_DEBUG_HOOK_STOP = JSSLOT_DEBUG_HOOK_START + HookCount,
+    JSSLOT_DEBUG_MEMORY_INSTANCE = JSSLOT_DEBUG_HOOK_STOP,
+    JSSLOT_DEBUG_DEBUGGEE_LINK,
+    JSSLOT_DEBUG_COUNT
+  };
+
+  // Bring DebugAPI::IsObserving into the Debugger namespace.
+  using IsObserving = DebugAPI::IsObserving;
+  static const IsObserving Observing = DebugAPI::Observing;
+  static const IsObserving NotObserving = DebugAPI::NotObserving;
+
+  // Return true if the given realm is a debuggee of this debugger,
+  // false otherwise.
+  bool isDebuggeeUnbarriered(const Realm* realm) const;
+
+  // Return true if this Debugger observed a debuggee that participated in the
+  // GC identified by the given GC number. Return false otherwise.
+  // May return false negatives if we have hit OOM.
+  bool observedGC(uint64_t majorGCNumber) const {
+    return observedGCs.has(majorGCNumber);
+  }
+
+  // Notify this Debugger that one or more of its debuggees is participating
+  // in the GC identified by the given GC number.
+  bool debuggeeIsBeingCollected(uint64_t majorGCNumber) {
+    return observedGCs.put(majorGCNumber);
+  }
+
+  static SavedFrame* getObjectAllocationSite(JSObject& obj);
+
+  struct AllocationsLogEntry {
+    AllocationsLogEntry(HandleObject frame, mozilla::TimeStamp when,
+                        const char* className, size_t size, bool inNursery)
+        : frame(frame),
+          when(when),
+          className(className),
+          size(size),
+          inNursery(inNursery) {
+      MOZ_ASSERT_IF(frame, UncheckedUnwrap(frame)->is<SavedFrame>() ||
+                               IsDeadProxyObject(frame));
+    }
+
+    HeapPtr<JSObject*> frame;
+    mozilla::TimeStamp when;
+    const char* className;
+    size_t size;
+    bool inNursery;
+
+    void trace(JSTracer* trc) {
+      TraceNullableEdge(trc, &frame, "Debugger::AllocationsLogEntry::frame");
+    }
+  };
+
+ private:
+  HeapPtrNativeObject object; /* The Debugger object. Strong reference. */
+  WeakGlobalObjectSet
+      debuggees; /* Debuggee globals. Cross-compartment weak references. */
+  JS::ZoneSet debuggeeZones; /* Set of zones that we have debuggees in. */
+  HeapPtrObject uncaughtExceptionHook; /* Strong reference. */
+  bool allowUnobservedAsmJS;
+
+  // Whether to enable code coverage on the Debuggee.
+  bool collectCoverageInfo;
+
+  template <typename T>
+  struct DebuggerLinkAccess {
+    static mozilla::DoublyLinkedListElement<T>& Get(T* aThis) {
+      return aThis->debuggerLink;
+    }
+  };
+
+  // List of all js::Breakpoints in this debugger.
+  using BreakpointList =
+      mozilla::DoublyLinkedList<js::Breakpoint,
+                                DebuggerLinkAccess<js::Breakpoint>>;
+  BreakpointList breakpoints;
+
+  // The set of GC numbers for which one or more of this Debugger's observed
+  // debuggees participated in.
+  using GCNumberSet =
+      HashSet<uint64_t, DefaultHasher<uint64_t>, ZoneAllocPolicy>;
+  GCNumberSet observedGCs;
+
+  using AllocationsLog = js::TraceableFifo<AllocationsLogEntry>;
+
+  AllocationsLog allocationsLog;
+  bool trackingAllocationSites;
+  double allocationSamplingProbability;
+  size_t maxAllocationsLogLength;
+  bool allocationsLogOverflowed;
+
+  static const size_t DEFAULT_MAX_LOG_LENGTH = 5000;
+
+  MOZ_MUST_USE bool appendAllocationSite(JSContext* cx, HandleObject obj,
+                                         HandleSavedFrame frame,
+                                         mozilla::TimeStamp when);
+
+  /*
+   * Recompute the set of debuggee zones based on the set of debuggee globals.
+   */
+  void recomputeDebuggeeZoneSet();
+
+  /*
+   * Return true if there is an existing object metadata callback for the
+   * given global's compartment that will prevent our instrumentation of
+   * allocations.
+   */
+  static bool cannotTrackAllocations(const GlobalObject& global);
+
+  /*
+   * Add allocations tracking for objects allocated within the given
+   * debuggee's compartment. The given debuggee global must be observed by at
+   * least one Debugger that is tracking allocations.
+   */
+  static MOZ_MUST_USE bool addAllocationsTracking(
+      JSContext* cx, Handle<GlobalObject*> debuggee);
+
+  /*
+   * Remove allocations tracking for objects allocated within the given
+   * global's compartment. This is a no-op if there are still Debuggers
+   * observing this global and who are tracking allocations.
+   */
+  static void removeAllocationsTracking(GlobalObject& global);
+
+  /*
+   * Add or remove allocations tracking for all debuggees.
+   */
+  MOZ_MUST_USE bool addAllocationsTrackingForAllDebuggees(JSContext* cx);
+  void removeAllocationsTrackingForAllDebuggees();
+
+  /*
+   * If this Debugger has a onNewGlobalObject handler, then
+   * this link is inserted into the list headed by
+   * JSRuntime::onNewGlobalObjectWatchers.
+   */
+  mozilla::DoublyLinkedListElement<Debugger> onNewGlobalObjectWatchersLink;
+
+  /*
+   * If this Debugger has a onGarbageCollection handler, then
+   * this link is inserted into the list headed by
+   * JSRuntime::onGarbageCollectionWatchers.
+   */
+  mozilla::DoublyLinkedListElement<Debugger> onGarbageCollectionWatchersLink;
+
+  /*
+   * Map from stack frames that are currently on the stack to Debugger.Frame
+   * instances.
+   *
+   * The keys are always live stack frames. We drop them from this map as
+   * soon as they leave the stack (see slowPathOnLeaveFrame) and in
+   * removeDebuggee.
+   *
+   * We don't trace the keys of this map (the frames are on the stack and
+   * thus necessarily live), but we do trace the values. It's like a WeakMap
+   * that way, but since stack frames are not gc-things, the implementation
+   * has to be different.
+   */
+  typedef HashMap<AbstractFramePtr, HeapPtr<DebuggerFrame*>,
+                  DefaultHasher<AbstractFramePtr>, ZoneAllocPolicy>
+      FrameMap;
+  FrameMap frames;
+
+  /*
+   * Map from generator objects to their Debugger.Frame instances.
+   *
+   * When a Debugger.Frame is created for a generator frame, it is added to
+   * this map and remains there for the lifetime of the generator, whether
+   * that frame is on the stack at the moment or not.  This is in addition to
+   * the entry in `frames` that exists as long as the generator frame is on
+   * the stack.
+   *
+   * We need to keep the Debugger.Frame object alive to deliver it to the
+   * onEnterFrame handler on resume, and to retain onStep and onPop hooks.
+   *
+   * An entry is present in this table when:
+   *  - both the debuggee generator object and the Debugger.Frame object exists
+   *  - the debuggee generator object belongs to a realm that is a debuggee of
+   *    the Debugger.Frame's owner.
+   *
+   * regardless of whether the frame is currently suspended. (This list is
+   * meant to explain why we update the table in the particular places where
+   * we do so.)
+   *
+   * An entry in this table exists if and only if the Debugger.Frame's
+   * GENERATOR_INFO_SLOT is set.
+   */
+  typedef DebuggerWeakMap<AbstractGeneratorObject, DebuggerFrame>
+      GeneratorWeakMap;
+  GeneratorWeakMap generatorFrames;
+
+  // An ephemeral map from BaseScript* to Debugger.Script instances.
+  using ScriptWeakMap = DebuggerWeakMap<BaseScript, DebuggerScript>;
+  ScriptWeakMap scripts;
+
+  using BaseScriptVector = JS::GCVector<BaseScript*>;
+
+  // The map from debuggee source script objects to their Debugger.Source
+  // instances.
+  typedef DebuggerWeakMap<ScriptSourceObject, DebuggerSource, true>
+      SourceWeakMap;
+  SourceWeakMap sources;
+
+  // The map from debuggee objects to their Debugger.Object instances.
+  typedef DebuggerWeakMap<JSObject, DebuggerObject> ObjectWeakMap;
+  ObjectWeakMap objects;
+
+  // The map from debuggee Envs to Debugger.Environment instances.
+  typedef DebuggerWeakMap<JSObject, DebuggerEnvironment> EnvironmentWeakMap;
+  EnvironmentWeakMap environments;
+
+  // The map from WasmInstanceObjects to synthesized Debugger.Script
+  // instances.
+  typedef DebuggerWeakMap<WasmInstanceObject, DebuggerScript>
+      WasmInstanceScriptWeakMap;
+  WasmInstanceScriptWeakMap wasmInstanceScripts;
+
+  // The map from WasmInstanceObjects to synthesized Debugger.Source
+  // instances.
+  typedef DebuggerWeakMap<WasmInstanceObject, DebuggerSource>
+      WasmInstanceSourceWeakMap;
+  WasmInstanceSourceWeakMap wasmInstanceSources;
+
+  // Keep track of tracelogger last drained identifiers to know if there are
+  // lost events.
+#ifdef NIGHTLY_BUILD
+  uint32_t traceLoggerLastDrainedSize;
+  uint32_t traceLoggerLastDrainedIteration;
+#endif
+  uint32_t traceLoggerScriptedCallsLastDrainedSize;
+  uint32_t traceLoggerScriptedCallsLastDrainedIteration;
+
+  class QueryBase;
+  class ScriptQuery;
+  class SourceQuery;
+  class ObjectQuery;
+
+  enum class FromSweep { No, Yes };
+
+  MOZ_MUST_USE bool addDebuggeeGlobal(JSContext* cx, Handle<GlobalObject*> obj);
+  void removeDebuggeeGlobal(JSFreeOp* fop, GlobalObject* global,
+                            WeakGlobalObjectSet::Enum* debugEnum,
+                            FromSweep fromSweep);
+
+  /*
+   * Handle the result of a hook that is expected to return a resumption
+   * value <https://wiki.mozilla.org/Debugger#Resumption_Values>. This is
+   * called when we return from a debugging hook to debuggee code.
+   *
+   * If `success` is false, the hook failed. If an exception is pending in
+   * ar.context(), attempt to handle it via the uncaught exception hook,
+   * otherwise report it to the AutoRealm's global.
+   *
+   * If `success` is true, there must be no exception pending in ar.context().
+   * `rv` may be:
+   *
+   *     undefined - Set `resultMode` to `ResumeMode::Continue` to continue
+   *         execution normally.
+   *
+   *     {return: value} or {throw: value} - Call unwrapDebuggeeValue to
+   *         unwrap `value`. Store the result in `vp` and set `resultMode` to
+   *         `ResumeMode::Return` or `ResumeMode::Throw`. The interpreter
+   *         will force the current frame to return or throw an exception.
+   *
+   *     null - Set `resultMode` to `ResumeMode::Terminate` to terminate the
+   *         debuggee with an uncatchable error.
+   *
+   *     anything else - Make a new TypeError the pending exception and
+   *         attempt to handle it with the uncaught exception handler.
+   */
+  MOZ_MUST_USE bool processHandlerResult(JSContext* cx, bool success,
+                                         HandleValue rv, AbstractFramePtr frame,
+                                         jsbytecode* pc, ResumeMode& resultMode,
+                                         MutableHandleValue vp);
+
+  MOZ_MUST_USE bool processParsedHandlerResult(
+      JSContext* cx, AbstractFramePtr frame, jsbytecode* pc, bool success,
+      ResumeMode resumeMode, HandleValue value, ResumeMode& resultMode,
+      MutableHandleValue vp);
+
+  /**
+   * Given a resumption return value from a hook, parse and validate it based
+   * on the given frame, and split the result into a ResumeMode and Value.
+   */
+  MOZ_MUST_USE bool prepareResumption(JSContext* cx, AbstractFramePtr frame,
+                                      jsbytecode* pc, ResumeMode& resumeMode,
+                                      MutableHandleValue vp);
+
+  /**
+   * If there is a pending exception and a handler, call the handler with the
+   * exception so that it can attempt to resolve the error.
+   */
+  MOZ_MUST_USE bool callUncaughtExceptionHandler(JSContext* cx,
+                                                 MutableHandleValue vp);
+
+  /**
+   * If the context has a pending exception, report it to the current global.
+   */
+  void reportUncaughtException(JSContext* cx);
+
+  /*
+   * Call the uncaught exception handler if there is one, returning true
+   * if it handled the error, or false otherwise.
+   */
+  MOZ_MUST_USE bool handleUncaughtException(JSContext* cx);
+
+  GlobalObject* unwrapDebuggeeArgument(JSContext* cx, const Value& v);
+
+  static void traceObject(JSTracer* trc, JSObject* obj);
+
+  void trace(JSTracer* trc);
+
+  void traceForMovingGC(JSTracer* trc);
+  void traceCrossCompartmentEdges(JSTracer* tracer);
+
+ private:
+  template <typename F>
+  void forEachWeakMap(const F& f);
+
+  static MOZ_MUST_USE bool getHookImpl(JSContext* cx, const CallArgs& args,
+                                       Debugger& dbg, Hook which);
+  static MOZ_MUST_USE bool setHookImpl(JSContext* cx, const CallArgs& args,
+                                       Debugger& dbg, Hook which);
+
+  static MOZ_MUST_USE bool getGarbageCollectionHook(JSContext* cx,
+                                                    const CallArgs& args,
+                                                    Debugger& dbg);
+  static MOZ_MUST_USE bool setGarbageCollectionHook(JSContext* cx,
+                                                    const CallArgs& args,
+                                                    Debugger& dbg);
+
+  static bool isCompilableUnit(JSContext* cx, unsigned argc, Value* vp);
+  static bool recordReplayProcessKind(JSContext* cx, unsigned argc, Value* vp);
+  static bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+
+  static const JSPropertySpec properties[];
+  static const JSFunctionSpec methods[];
+  static const JSFunctionSpec static_methods[];
+
+  /**
+   * Suspend the DebuggerFrame, clearing on-stack data but leaving it linked
+   * with the AbstractGeneratorObject so it can be re-used later.
+   */
+  static void suspendGeneratorDebuggerFrames(JSContext* cx,
+                                             AbstractFramePtr frame);
+
+  /**
+   * Terminate the DebuggerFrame, clearing all data associated with the frame
+   * so that it cannot be used to introspect stack frame data.
+   */
+  static void terminateDebuggerFrames(JSContext* cx, AbstractFramePtr frame);
+
+  /**
+   * Terminate a given DebuggerFrame, removing all internal state and all
+   * references to the frame from the Debugger itself. If the frame is being
+   * terminated while 'frames' or 'generatorFrames' are being iterated, pass a
+   * pointer to the iteration Enum to remove the entry and ensure that iteration
+   * behaves properly.
+   *
+   * The AbstractFramePtr may be omited in a call so long as it is either
+   * called again later with the correct 'frame', or the frame itself has never
+   * had on-stack data or a 'frames' entry and has never had an onStep handler.
+   */
+  static void terminateDebuggerFrame(
+      JSFreeOp* fop, Debugger* dbg, DebuggerFrame* dbgFrame,
+      AbstractFramePtr frame, FrameMap::Enum* maybeFramesEnum = nullptr,
+      GeneratorWeakMap::Enum* maybeGeneratorFramesEnum = nullptr);
+
+  static bool updateExecutionObservabilityOfFrames(
+      JSContext* cx, const DebugAPI::ExecutionObservableSet& obs,
+      IsObserving observing);
+  static bool updateExecutionObservabilityOfScripts(
+      JSContext* cx, const DebugAPI::ExecutionObservableSet& obs,
+      IsObserving observing);
+  static bool updateExecutionObservability(
+      JSContext* cx, DebugAPI::ExecutionObservableSet& obs,
+      IsObserving observing);
+
+  template <typename FrameFn /* void (Debugger*, DebuggerFrame*) */>
+  static void forEachOnStackDebuggerFrame(AbstractFramePtr frame, FrameFn fn);
+  template <typename FrameFn /* void (Debugger*, DebuggerFrame*) */>
+  static void forEachOnStackOrSuspendedDebuggerFrame(JSContext* cx,
+                                                     AbstractFramePtr frame,
+                                                     FrameFn fn);
+
+  /*
+   * Return a vector containing all Debugger.Frame instances referring to
+   * |frame|. |global| is |frame|'s global object; if nullptr or omitted, we
+   * compute it ourselves from |frame|.
+   */
+  using DebuggerFrameVector = GCVector<DebuggerFrame*>;
+  static MOZ_MUST_USE bool getDebuggerFrames(
+      AbstractFramePtr frame, MutableHandle<DebuggerFrameVector> frames);
+
+ public:
+  // Public for DebuggerScript::setBreakpoint.
+  static MOZ_MUST_USE bool ensureExecutionObservabilityOfScript(
+      JSContext* cx, JSScript* script);
+
+  // Whether the Debugger instance needs to observe all non-AOT JS
+  // execution of its debugees.
+  IsObserving observesAllExecution() const;
+
+  // Whether the Debugger instance needs to observe AOT-compiled asm.js
+  // execution of its debuggees.
+  IsObserving observesAsmJS() const;
+
+  // Whether the Debugger instance needs to observe coverage of any JavaScript
+  // execution.
+  IsObserving observesCoverage() const;
+
+  // Whether the Debugger instance needs to observe native call invocations.
+  IsObserving observesNativeCalls() const;
+
+ private:
+  static MOZ_MUST_USE bool ensureExecutionObservabilityOfFrame(
+      JSContext* cx, AbstractFramePtr frame);
+  static MOZ_MUST_USE bool ensureExecutionObservabilityOfRealm(
+      JSContext* cx, JS::Realm* realm);
+
+  static bool hookObservesAllExecution(Hook which);
+
+  MOZ_MUST_USE bool updateObservesAllExecutionOnDebuggees(
+      JSContext* cx, IsObserving observing);
+  MOZ_MUST_USE bool updateObservesCoverageOnDebuggees(JSContext* cx,
+                                                      IsObserving observing);
+  void updateObservesAsmJSOnDebuggees(IsObserving observing);
+
+  JSObject* getHook(Hook hook) const;
+  bool hasAnyLiveHooks() const;
+  inline bool isHookCallAllowed(JSContext* cx) const;
+
+  static void slowPathPromiseHook(JSContext* cx, Hook hook,
+                                  Handle<PromiseObject*> promise);
+
+  template <typename HookIsEnabledFun /* bool (Debugger*) */,
+            typename FireHookFun /* void (Debugger*) */>
+  static void dispatchQuietHook(JSContext* cx, HookIsEnabledFun hookIsEnabled,
+                                FireHookFun fireHook);
+  template <
+      typename HookIsEnabledFun /* bool (Debugger*) */, typename FireHookFun /* bool (Debugger*, ResumeMode&, MutableHandleValue) */>
+  static MOZ_MUST_USE bool dispatchResumptionHook(
+      JSContext* cx, AbstractFramePtr frame, HookIsEnabledFun hookIsEnabled,
+      FireHookFun fireHook);
+
+  template <typename RunImpl /* bool () */>
+  MOZ_MUST_USE bool enterDebuggerHook(JSContext* cx, RunImpl runImpl) {
+    if (!isHookCallAllowed(cx)) {
+      return true;
+    }
+
+    AutoRealm ar(cx, object);
+
+    if (!runImpl()) {
+      // We do not want errors within one hook to effect errors in other hooks,
+      // so the only errors that we allow to propagate out of a debugger hook
+      // are OOM errors and general terminations.
+      if (!cx->isExceptionPending() || cx->isThrowingOutOfMemory()) {
+        return false;
+      }
+
+      reportUncaughtException(cx);
+    }
+    MOZ_ASSERT(!cx->isExceptionPending());
+    return true;
+  }
+
+  MOZ_MUST_USE bool fireDebuggerStatement(JSContext* cx, ResumeMode& resumeMode,
+                                          MutableHandleValue vp);
+  MOZ_MUST_USE bool fireExceptionUnwind(JSContext* cx, HandleValue exc,
+                                        ResumeMode& resumeMode,
+                                        MutableHandleValue vp);
+  MOZ_MUST_USE bool fireEnterFrame(JSContext* cx, ResumeMode& resumeMode,
+                                   MutableHandleValue vp);
+  MOZ_MUST_USE bool fireNativeCall(JSContext* cx, const CallArgs& args,
+                                   CallReason reason, ResumeMode& resumeMode,
+                                   MutableHandleValue vp);
+  MOZ_MUST_USE bool fireNewGlobalObject(JSContext* cx,
+                                        Handle<GlobalObject*> global);
+  MOZ_MUST_USE bool firePromiseHook(JSContext* cx, Hook hook,
+                                    HandleObject promise);
+
+  DebuggerScript* newVariantWrapper(JSContext* cx,
+                                    Handle<DebuggerScriptReferent> referent) {
+    return newDebuggerScript(cx, referent);
+  }
+  DebuggerSource* newVariantWrapper(JSContext* cx,
+                                    Handle<DebuggerSourceReferent> referent) {
+    return newDebuggerSource(cx, referent);
+  }
+
+  /*
+   * Helper function to help wrap Debugger objects whose referents may be
+   * variants. Currently Debugger.Script and Debugger.Source referents may
+   * be variants.
+   *
+   * Prefer using wrapScript, wrapWasmScript, wrapSource, and wrapWasmSource
+   * whenever possible.
+   */
+  template <typename ReferentType, typename Map>
+  typename Map::WrapperType* wrapVariantReferent(
+      JSContext* cx, Map& map,
+      Handle<typename Map::WrapperType::ReferentVariant> referent);
+  DebuggerScript* wrapVariantReferent(JSContext* cx,
+                                      Handle<DebuggerScriptReferent> referent);
+  DebuggerSource* wrapVariantReferent(JSContext* cx,
+                                      Handle<DebuggerSourceReferent> referent);
+
+  /*
+   * Allocate and initialize a Debugger.Script instance whose referent is
+   * |referent|.
+   */
+  DebuggerScript* newDebuggerScript(JSContext* cx,
+                                    Handle<DebuggerScriptReferent> referent);
+
+  /*
+   * Allocate and initialize a Debugger.Source instance whose referent is
+   * |referent|.
+   */
+  DebuggerSource* newDebuggerSource(JSContext* cx,
+                                    Handle<DebuggerSourceReferent> referent);
+
+  /*
+   * Receive a "new script" event from the engine. A new script was compiled
+   * or deserialized.
+   */
+  MOZ_MUST_USE bool fireNewScript(
+      JSContext* cx, Handle<DebuggerScriptReferent> scriptReferent);
+
+  /*
+   * Receive a "garbage collection" event from the engine. A GC cycle with the
+   * given data was recently completed.
+   */
+  MOZ_MUST_USE bool fireOnGarbageCollectionHook(
+      JSContext* cx, const JS::dbg::GarbageCollectionEvent::Ptr& gcData);
+
+  inline Breakpoint* firstBreakpoint() const;
+
+  static MOZ_MUST_USE bool replaceFrameGuts(JSContext* cx,
+                                            AbstractFramePtr from,
+                                            AbstractFramePtr to,
+                                            ScriptFrameIter& iter);
+
+ public:
+  Debugger(JSContext* cx, NativeObject* dbg);
+  ~Debugger();
+
+  inline const js::HeapPtrNativeObject& toJSObject() const;
+  inline js::HeapPtrNativeObject& toJSObjectRef();
+  static inline Debugger* fromJSObject(const JSObject* obj);
+
+#ifdef DEBUG
+  static bool isChildJSObject(JSObject* obj);
+#endif
+
+  Zone* zone() const { return toJSObject()->zone(); }
+
+  bool hasMemory() const;
+  DebuggerMemory& memory() const;
+
+  WeakGlobalObjectSet::Range allDebuggees() const { return debuggees.all(); }
+
+#ifdef DEBUG
+  static bool isDebuggerCrossCompartmentEdge(JSObject* obj,
+                                             const js::gc::Cell* cell);
+#endif
+
+  static bool hasLiveHook(GlobalObject* global, Hook which);
+
+  /*** Functions for use by Debugger.cpp. *********************************/
+
+  inline bool observesEnterFrame() const;
+  inline bool observesNewScript() const;
+  inline bool observesNewGlobalObject() const;
+  inline bool observesGlobal(GlobalObject* global) const;
+  bool observesFrame(AbstractFramePtr frame) const;
+  bool observesFrame(const FrameIter& iter) const;
+  bool observesScript(JSScript* script) const;
+  bool observesWasm(wasm::Instance* instance) const;
+
+  /*
+   * If env is nullptr, call vp->setNull() and return true. Otherwise, find
+   * or create a Debugger.Environment object for the given Env. On success,
+   * store the Environment object in *vp and return true.
+   */
+  MOZ_MUST_USE bool wrapEnvironment(JSContext* cx, Handle<Env*> env,
+                                    MutableHandleValue vp);
+  MOZ_MUST_USE bool wrapEnvironment(JSContext* cx, Handle<Env*> env,
+                                    MutableHandleDebuggerEnvironment result);
+
+  /*
+   * Like cx->compartment()->wrap(cx, vp), but for the debugger realm.
+   *
+   * Preconditions: *vp is a value from a debuggee realm; cx is in the
+   * debugger's compartment.
+   *
+   * If *vp is an object, this produces a (new or existing) Debugger.Object
+   * wrapper for it. Otherwise this is the same as Compartment::wrap.
+   *
+   * If *vp is a magic JS_OPTIMIZED_OUT value, this produces a plain object
+   * of the form { optimizedOut: true }.
+   *
+   * If *vp is a magic JS_OPTIMIZED_ARGUMENTS value signifying missing
+   * arguments, this produces a plain object of the form { missingArguments:
+   * true }.
+   *
+   * If *vp is a magic JS_UNINITIALIZED_LEXICAL value signifying an
+   * unaccessible uninitialized binding, this produces a plain object of the
+   * form { uninitialized: true }.
+   */
+  MOZ_MUST_USE bool wrapDebuggeeValue(JSContext* cx, MutableHandleValue vp);
+  MOZ_MUST_USE bool wrapDebuggeeObject(JSContext* cx, HandleObject obj,
+                                       MutableHandleDebuggerObject result);
+  MOZ_MUST_USE bool wrapNullableDebuggeeObject(
+      JSContext* cx, HandleObject obj, MutableHandleDebuggerObject result);
+
+  /*
+   * Unwrap a Debug.Object, without rewrapping it for any particular debuggee
+   * compartment.
+   *
+   * Preconditions: cx is in the debugger compartment. *vp is a value in that
+   * compartment. (*vp should be a "debuggee value", meaning it is the
+   * debugger's reflection of a value in the debuggee.)
+   *
+   * If *vp is a Debugger.Object, store the referent in *vp. Otherwise, if *vp
+   * is an object, throw a TypeError, because it is not a debuggee
+   * value. Otherwise *vp is a primitive, so leave it alone.
+   *
+   * When passing values from the debuggee to the debugger:
+   *     enter debugger compartment;
+   *     call wrapDebuggeeValue;  // compartment- and debugger-wrapping
+   *
+   * When passing values from the debugger to the debuggee:
+   *     call unwrapDebuggeeValue;  // debugger-unwrapping
+   *     enter debuggee realm;
+   *     call cx->compartment()->wrap;  // compartment-rewrapping
+   *
+   * (Extreme nerd sidebar: Unwrapping happens in two steps because there are
+   * two different kinds of symmetry at work: regardless of which direction
+   * we're going, we want any exceptions to be created and thrown in the
+   * debugger compartment--mirror symmetry. But compartment wrapping always
+   * happens in the target compartment--rotational symmetry.)
+   */
+  MOZ_MUST_USE bool unwrapDebuggeeValue(JSContext* cx, MutableHandleValue vp);
+  MOZ_MUST_USE bool unwrapDebuggeeObject(JSContext* cx,
+                                         MutableHandleObject obj);
+  MOZ_MUST_USE bool unwrapPropertyDescriptor(
+      JSContext* cx, HandleObject obj, MutableHandle<PropertyDescriptor> desc);
+
+  /*
+   * Store the Debugger.Frame object for iter in *vp/result.
+   *
+   * If this Debugger does not already have a Frame object for the frame
+   * `iter` points to, a new Frame object is created, and `iter`'s private
+   * data is copied into it.
+   */
+  MOZ_MUST_USE bool getFrame(JSContext* cx, const FrameIter& iter,
+                             MutableHandleValue vp);
+  MOZ_MUST_USE bool getFrame(JSContext* cx, MutableHandleDebuggerFrame result);
+  MOZ_MUST_USE bool getFrame(JSContext* cx, const FrameIter& iter,
+                             MutableHandleDebuggerFrame result);
+  MOZ_MUST_USE bool getFrame(JSContext* cx,
+                             Handle<AbstractGeneratorObject*> genObj,
+                             MutableHandleDebuggerFrame result);
+
+  /*
+   * Return the Debugger.Script object for |script|, or create a new one if
+   * needed. The context |cx| must be in the debugger realm; |script| must be
+   * a script in a debuggee realm.
+   */
+  DebuggerScript* wrapScript(JSContext* cx, Handle<BaseScript*> script);
+
+  /*
+   * Return the Debugger.Script object for |wasmInstance| (the toplevel
+   * script), synthesizing a new one if needed. The context |cx| must be in
+   * the debugger compartment; |wasmInstance| must be a WasmInstanceObject in
+   * the debuggee realm.
+   */
+  DebuggerScript* wrapWasmScript(JSContext* cx,
+                                 Handle<WasmInstanceObject*> wasmInstance);
+
+  /*
+   * Return the Debugger.Source object for |source|, or create a new one if
+   * needed. The context |cx| must be in the debugger compartment; |source|
+   * must be a script source object in a debuggee realm.
+   */
+  DebuggerSource* wrapSource(JSContext* cx,
+                             js::HandleScriptSourceObject source);
+
+  /*
+   * Return the Debugger.Source object for |wasmInstance| (the entire module),
+   * synthesizing a new one if needed. The context |cx| must be in the
+   * debugger compartment; |wasmInstance| must be a WasmInstanceObject in the
+   * debuggee realm.
+   */
+  DebuggerSource* wrapWasmSource(JSContext* cx,
+                                 Handle<WasmInstanceObject*> wasmInstance);
+
+  DebuggerDebuggeeLink* getDebuggeeLink();
+
+ private:
+  Debugger(const Debugger&) = delete;
+  Debugger& operator=(const Debugger&) = delete;
+};
+
+// Specialize InternalBarrierMethods so we can have WeakHeapPtr<Debugger*>.
+template <>
+struct InternalBarrierMethods<Debugger*> {
+  static bool isMarkable(Debugger* dbg) { return dbg->toJSObject(); }
+
+  static void postBarrier(Debugger** vp, Debugger* prev, Debugger* next) {}
+
+  static void readBarrier(Debugger* dbg) {
+    InternalBarrierMethods<JSObject*>::readBarrier(dbg->toJSObject());
+  }
+
+#ifdef DEBUG
+  static void assertThingIsNotGray(Debugger* dbg) {}
+#endif
+};
+
+/**
+ * This class exists for one specific reason. If a given Debugger object is in
+ * a state where:
+ *
+ *   a) nothing in the system has a reference to the object
+ *   b) the debugger is currently attached to a live debuggee
+ *   c) the debugger has hooks like 'onEnterFrame'
+ *
+ * then we don't want the GC to delete the Debugger, because the system could
+ * still call the hooks. This means we need to ensure that, whenever the global
+ * gets marked, the Debugger will get marked as well. Critically, we _only_
+ * want that to happen if the debugger has hooks. If it doesn't, then GCing
+ * the debugger is the right think to do.
+ *
+ * Note that there are _other_ cases where the debugger may be held live, but
+ * those are not addressed by this case.
+ *
+ * To accomplish this, we use a bit of roundabout link approach. Both the
+ * Debugger and the debuggees can reach the link object:
+ *
+ *   Debugger  -> DebuggerDebuggeeLink  <- CCW <- Debuggee Global #1
+ *      |                  |    ^   ^---<- CCW <- Debuggee Global #2
+ *      \--<<-optional-<<--/     \------<- CCW <- Debuggee Global #3
+ *
+ * and critically, the Debugger is able to conditionally add or remove the link
+ * going from the DebuggerDebuggeeLink _back_ to the Debugger. When this link
+ * exists, the GC can trace all the way from the global to the Debugger,
+ * meaning that any Debugger with this link will be kept alive as long as any
+ * of its debuggees are alive.
+ */
+class DebuggerDebuggeeLink : public NativeObject {
+ private:
+  enum {
+    DEBUGGER_LINK_SLOT,
+    RESERVED_SLOTS,
+  };
+
+ public:
+  static const JSClass class_;
+
+  void setLinkSlot(Debugger& dbg);
+  void clearLinkSlot();
+};
+
+/*
+ * A Handler represents a Debugger API reflection object's handler function,
+ * like a Debugger.Frame's onStep handler. These handler functions are called by
+ * the Debugger API to notify the user of certain events. For each event type,
+ * we define a separate subclass of Handler.
+ *
+ * When a reflection object accepts a Handler, it calls its 'hold' method; and
+ * if the Handler is replaced by another, or the reflection object is finalized,
+ * the reflection object calls the Handler's 'drop' method. The reflection
+ * object does not otherwise manage the Handler's lifetime, say, by calling its
+ * destructor or freeing its memory. A simple Handler implementation might have
+ * an empty 'hold' method, and have its 'drop' method delete the Handler. A more
+ * complex Handler might process many kinds of events, and thus inherit from
+ * many Handler subclasses and be held by many reflection objects
+ * simultaneously; a handler like this could use 'hold' and 'drop' to manage a
+ * reference count.
+ *
+ * To support SpiderMonkey's memory use tracking, 'hold' and 'drop' also require
+ * a pointer to the owning reflection object, so that the Holder implementation
+ * can properly report changes in ownership to functions using the
+ * js::gc::MemoryUse categories.
+ */
+struct Handler {
+  virtual ~Handler() = default;
+
+  /*
+   * If this Handler is a reference to a callable JSObject, return that
+   * JSObject. Otherwise, this method returns nullptr.
+   *
+   * The JavaScript getters for handler properties on reflection objects use
+   * this method to obtain the callable the handler represents. When a Handler's
+   * 'object' method returns nullptr, that handler is simply not visible to
+   * JavaScript.
+   */
+  virtual JSObject* object() const = 0;
+
+  /* Report that this Handler is now held by owner. See comment above. */
+  virtual void hold(JSObject* owner) = 0;
+
+  /* Report that this Handler is no longer held by owner. See comment above. */
+  virtual void drop(JSFreeOp* fop, JSObject* owner) = 0;
+
+  /*
+   * Trace the reference to the handler. This method will be called by the
+   * reflection object holding this Handler whenever the former is traced.
+   */
+  virtual void trace(JSTracer* tracer) = 0;
+
+  /* Allocation size in bytes for memory accounting purposes. */
+  virtual size_t allocSize() const = 0;
+};
+
+class JSBreakpointSite;
+class WasmBreakpointSite;
+
+/**
+ * Breakpoint GC rules:
+ *
+ * BreakpointSites and Breakpoints are owned by the code in which they are set.
+ * Tracing a JSScript or WasmInstance traces all BreakpointSites set in it,
+ * which traces all Breakpoints; and if the code is garbage collected, the
+ * BreakpointSite and the Breakpoints set at it are freed as well. Doing so is
+ * not observable to JS, since the handlers would never fire, and there is no
+ * way to enumerate all breakpoints without specifying a specific script, in
+ * which case it must not have been GC'd.
+ *
+ * Although BreakpointSites and Breakpoints are not GC things, they should be
+ * treated as belonging to the code's compartment. This means that the
+ * BreakpointSite concrete subclasses' pointers to the code are not
+ * cross-compartment references, but a Breakpoint's pointers to its handler and
+ * owning Debugger are cross-compartment references, and go through
+ * cross-compartment wrappers.
+ */
+
+/**
+ * A location in a JSScript or WasmInstance at which we have breakpoints. A
+ * BreakpointSite owns a linked list of all the breakpoints set at its location.
+ * In general, this list contains breakpoints set by multiple Debuggers in
+ * various compartments.
+ *
+ * BreakpointSites are created only as needed, for locations at which
+ * breakpoints are currently set. When the last breakpoint is removed from a
+ * location, the BreakpointSite is removed as well.
+ *
+ * This is an abstract base class, with subclasses specialized for the different
+ * sorts of code a breakpoint might be set in. JSBreakpointSite manages sites in
+ * JSScripts, and WasmBreakpointSite manages sites in WasmInstances.
+ */
+class BreakpointSite {
+  friend class DebugAPI;
+  friend class Breakpoint;
+  friend class Debugger;
+
+ private:
+  template <typename T>
+  struct SiteLinkAccess {
+    static mozilla::DoublyLinkedListElement<T>& Get(T* aThis) {
+      return aThis->siteLink;
+    }
+  };
+
+  // List of all js::Breakpoints at this instruction.
+  using BreakpointList =
+      mozilla::DoublyLinkedList<js::Breakpoint, SiteLinkAccess<js::Breakpoint>>;
+  BreakpointList breakpoints;
+
+ protected:
+  BreakpointSite() = default;
+  virtual ~BreakpointSite() = default;
+  void finalize(JSFreeOp* fop);
+  virtual gc::Cell* owningCell() = 0;
+
+ public:
+  Breakpoint* firstBreakpoint() const;
+  bool hasBreakpoint(Breakpoint* bp);
+
+  bool isEmpty() const;
+  virtual void trace(JSTracer* trc);
+  virtual void remove(JSFreeOp* fop) = 0;
+  void destroyIfEmpty(JSFreeOp* fop) {
+    if (isEmpty()) {
+      remove(fop);
+    }
+  }
+  virtual Realm* realm() const = 0;
+};
+
+/*
+ * A breakpoint set at a given BreakpointSite, indicating the owning debugger
+ * and the handler object. A Breakpoint is a member of two linked lists: its
+ * owning debugger's list and its site's list.
+ */
+class Breakpoint {
+  friend class DebugAPI;
+  friend class Debugger;
+  friend class BreakpointSite;
+
+ public:
+  /* Our owning debugger. */
+  Debugger* const debugger;
+
+  /**
+   * A cross-compartment wrapper for our owning debugger's object, a CCW in the
+   * code's compartment to the Debugger object in its own compartment. Holding
+   * this lets the GC know about the effective cross-compartment reference from
+   * the code to the debugger; see "Breakpoint GC Rules", above.
+   *
+   * This is almost redundant with the `debugger` field, except that we need
+   * access to our owning `Debugger` regardless of the relative privilege levels
+   * of debugger and debuggee, regardless of whether we're in the midst of a GC,
+   * and so on - unwrapping is just too entangled.
+   */
+  const HeapPtr<JSObject*> wrappedDebugger;
+
+  /* The site at which we're inserted. */
+  BreakpointSite* const site;
+
+ private:
+  /**
+   * The breakpoint handler object, via a cross-compartment wrapper in the
+   * code's compartment.
+   *
+   * Although eventually we would like this to be a `js::Handler` instance, for
+   * now it is just cross-compartment wrapper for the JS object supplied to
+   * `setBreakpoint`, hopefully with a callable `hit` property.
+   */
+  const HeapPtr<JSObject*> handler;
+
+  /**
+   * Link elements for each list this breakpoint can be in.
+   */
+  mozilla::DoublyLinkedListElement<Breakpoint> debuggerLink;
+  mozilla::DoublyLinkedListElement<Breakpoint> siteLink;
+
+  void trace(JSTracer* trc);
+
+ public:
+  Breakpoint(Debugger* debugger, HandleObject wrappedDebugger,
+             BreakpointSite* site, HandleObject handler);
+
+  enum MayDestroySite { False, True };
+
+  /**
+   * Unlink this breakpoint from its Debugger's and and BreakpointSite's lists,
+   * and free its memory.
+   *
+   * This is the low-level primitive shared by breakpoint removal and script
+   * finalization code. It is only concerned with cleaning up this Breakpoint;
+   * it does not check for now-empty BreakpointSites, unneeded DebugScripts, or
+   * the like.
+   */
+  void delete_(JSFreeOp* fop);
+
+  /**
+   * Remove this breakpoint. Unlink it from its Debugger's and BreakpointSite's
+   * lists, and if the BreakpointSite is now empty, clean that up and update JIT
+   * code as necessary.
+   */
+  void remove(JSFreeOp* fop);
+
+  Breakpoint* nextInDebugger();
+  Breakpoint* nextInSite();
+  JSObject* getHandler() const { return handler; }
+};
+
+class JSBreakpointSite : public BreakpointSite {
+ public:
+  const HeapPtr<JSScript*> script;
+  jsbytecode* const pc;
+
+ public:
+  JSBreakpointSite(JSScript* script, jsbytecode* pc);
+
+  void trace(JSTracer* trc) override;
+  void delete_(JSFreeOp* fop);
+  void remove(JSFreeOp* fop) override;
+  Realm* realm() const override;
+
+ private:
+  gc::Cell* owningCell() override;
+};
+
+class WasmBreakpointSite : public BreakpointSite {
+ public:
+  const HeapPtr<WasmInstanceObject*> instanceObject;
+  uint32_t offset;
+
+ public:
+  WasmBreakpointSite(WasmInstanceObject* instanceObject, uint32_t offset);
+
+  void trace(JSTracer* trc) override;
+  void delete_(JSFreeOp* fop);
+  void remove(JSFreeOp* fop) override;
+  Realm* realm() const override;
+
+ private:
+  gc::Cell* owningCell() override;
+};
+
+Breakpoint* Debugger::firstBreakpoint() const {
+  if (breakpoints.isEmpty()) {
+    return nullptr;
+  }
+  return &(*breakpoints.begin());
+}
+
+const js::HeapPtrNativeObject& Debugger::toJSObject() const {
+  MOZ_ASSERT(object);
+  return object;
+}
+
+js::HeapPtrNativeObject& Debugger::toJSObjectRef() {
+  MOZ_ASSERT(object);
+  return object;
+}
+
+bool Debugger::observesEnterFrame() const { return getHook(OnEnterFrame); }
+
+bool Debugger::observesNewScript() const { return getHook(OnNewScript); }
+
+bool Debugger::observesNewGlobalObject() const {
+  return getHook(OnNewGlobalObject);
+}
+
+bool Debugger::observesGlobal(GlobalObject* global) const {
+  WeakHeapPtr<GlobalObject*> debuggee(global);
+  return debuggees.has(debuggee);
+}
+
+MOZ_MUST_USE bool ReportObjectRequired(JSContext* cx);
+
+JSObject* IdVectorToArray(JSContext* cx, Handle<IdVector> ids);
+bool IsInterpretedNonSelfHostedFunction(JSFunction* fun);
+JSScript* GetOrCreateFunctionScript(JSContext* cx, HandleFunction fun);
+ArrayObject* GetFunctionParameterNamesArray(JSContext* cx, HandleFunction fun);
+bool ValueToIdentifier(JSContext* cx, HandleValue v, MutableHandleId id);
+bool ValueToStableChars(JSContext* cx, const char* fnname, HandleValue value,
+                        JS::AutoStableStringChars& stableChars);
+bool ParseEvalOptions(JSContext* cx, HandleValue value, EvalOptions& options);
+
+Result<Completion> DebuggerGenericEval(
+    JSContext* cx, const mozilla::Range<const char16_t> chars,
+    HandleObject bindings, const EvalOptions& options, Debugger* dbg,
+    HandleObject envArg, FrameIter* iter);
+
+bool ParseResumptionValue(JSContext* cx, HandleValue rval,
+                          ResumeMode& resumeMode, MutableHandleValue vp);
+
+#define JS_DEBUG_PSG(Name, Getter) \
+  JS_PSG(Name, CallData::ToNative<&CallData::Getter>, 0)
+
+#define JS_DEBUG_PSGS(Name, Getter, Setter)            \
+  JS_PSGS(Name, CallData::ToNative<&CallData::Getter>, \
+          CallData::ToNative<&CallData::Setter>, 0)
+
+#define JS_DEBUG_FN(Name, Method, NumArgs) \
+  JS_FN(Name, CallData::ToNative<&CallData::Method>, NumArgs, 0)
+
+} /* namespace js */
+
+#endif /* debugger_Debugger_h */
diff --git a/js/src/debugger/DebuggerMemory.cpp b/js/src/debugger/DebuggerMemory.cpp
new file mode 100644
index 0000000000..43ad1ea18e
--- /dev/null
+++ b/js/src/debugger/DebuggerMemory.cpp
@@ -0,0 +1,449 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/DebuggerMemory.h"
+
+#include "mozilla/Maybe.h"
+#include "mozilla/Vector.h"
+
+#include <stdlib.h>
+#include <utility>
+
+#include "builtin/MapObject.h"
+#include "debugger/Debugger.h"
+#include "gc/Marking.h"
+#include "js/AllocPolicy.h"
+#include "js/Debug.h"
+#include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
+#include "js/PropertySpec.h"
+#include "js/TracingAPI.h"
+#include "js/UbiNode.h"
+#include "js/UbiNodeCensus.h"
+#include "js/Utility.h"
+#include "vm/GlobalObject.h"
+#include "vm/JSContext.h"
+#include "vm/PlainObject.h"  // js::PlainObject
+#include "vm/Realm.h"
+#include "vm/SavedStacks.h"
+
+#include "debugger/Debugger-inl.h"
+#include "vm/NativeObject-inl.h"
+
+using namespace js;
+
+using mozilla::Maybe;
+using mozilla::Nothing;
+
+/* static */
+DebuggerMemory* DebuggerMemory::create(JSContext* cx, Debugger* dbg) {
+  Value memoryProtoValue =
+      dbg->object->getReservedSlot(Debugger::JSSLOT_DEBUG_MEMORY_PROTO);
+  RootedObject memoryProto(cx, &memoryProtoValue.toObject());
+  Rooted<DebuggerMemory*> memory(
+      cx, NewObjectWithGivenProto<DebuggerMemory>(cx, memoryProto));
+  if (!memory) {
+    return nullptr;
+  }
+
+  dbg->object->setReservedSlot(Debugger::JSSLOT_DEBUG_MEMORY_INSTANCE,
+                               ObjectValue(*memory));
+  memory->setReservedSlot(JSSLOT_DEBUGGER, ObjectValue(*dbg->object));
+
+  return memory;
+}
+
+Debugger* DebuggerMemory::getDebugger() {
+  const Value& dbgVal = getReservedSlot(JSSLOT_DEBUGGER);
+  return Debugger::fromJSObject(&dbgVal.toObject());
+}
+
+/* static */
+bool DebuggerMemory::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Source");
+  return false;
+}
+
+/* static */ const JSClass DebuggerMemory::class_ = {
+    "Memory", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(JSSLOT_COUNT)};
+
+/* static */
+DebuggerMemory* DebuggerMemory::checkThis(JSContext* cx, CallArgs& args) {
+  const Value& thisValue = args.thisv();
+
+  if (!thisValue.isObject()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_OBJECT_REQUIRED,
+                              InformalValueTypeName(thisValue));
+    return nullptr;
+  }
+
+  JSObject& thisObject = thisValue.toObject();
+  if (!thisObject.is<DebuggerMemory>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, class_.name, "method",
+                              thisObject.getClass()->name);
+    return nullptr;
+  }
+
+  // Check for Debugger.Memory.prototype, which has the same class as
+  // Debugger.Memory instances, however doesn't actually represent an instance
+  // of Debugger.Memory. It is the only object that is<DebuggerMemory>() but
+  // doesn't have a Debugger instance.
+  if (thisObject.as<DebuggerMemory>()
+          .getReservedSlot(JSSLOT_DEBUGGER)
+          .isUndefined()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, class_.name, "method",
+                              "prototype object");
+    return nullptr;
+  }
+
+  return &thisObject.as<DebuggerMemory>();
+}
+
+struct MOZ_STACK_CLASS DebuggerMemory::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  Handle<DebuggerMemory*> memory;
+
+  CallData(JSContext* cx, const CallArgs& args, Handle<DebuggerMemory*> memory)
+      : cx(cx), args(args), memory(memory) {}
+
+  // Accessor properties of Debugger.Memory.prototype.
+
+  bool setTrackingAllocationSites();
+  bool getTrackingAllocationSites();
+  bool setMaxAllocationsLogLength();
+  bool getMaxAllocationsLogLength();
+  bool setAllocationSamplingProbability();
+  bool getAllocationSamplingProbability();
+  bool getAllocationsLogOverflowed();
+  bool getOnGarbageCollection();
+  bool setOnGarbageCollection();
+
+  // Function properties of Debugger.Memory.prototype.
+
+  bool takeCensus();
+  bool drainAllocationsLog();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <DebuggerMemory::CallData::Method MyMethod>
+/* static */
+bool DebuggerMemory::CallData::ToNative(JSContext* cx, unsigned argc,
+                                        Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  Rooted<DebuggerMemory*> memory(cx, DebuggerMemory::checkThis(cx, args));
+  if (!memory) {
+    return false;
+  }
+
+  CallData data(cx, args, memory);
+  return (data.*MyMethod)();
+}
+
+static bool undefined(const CallArgs& args) {
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerMemory::CallData::setTrackingAllocationSites() {
+  if (!args.requireAtLeast(cx, "(set trackingAllocationSites)", 1)) {
+    return false;
+  }
+
+  Debugger* dbg = memory->getDebugger();
+  bool enabling = ToBoolean(args[0]);
+
+  if (enabling == dbg->trackingAllocationSites) {
+    return undefined(args);
+  }
+
+  dbg->trackingAllocationSites = enabling;
+
+  if (enabling) {
+    if (!dbg->addAllocationsTrackingForAllDebuggees(cx)) {
+      dbg->trackingAllocationSites = false;
+      return false;
+    }
+  } else {
+    dbg->removeAllocationsTrackingForAllDebuggees();
+  }
+
+  return undefined(args);
+}
+
+bool DebuggerMemory::CallData::getTrackingAllocationSites() {
+  args.rval().setBoolean(memory->getDebugger()->trackingAllocationSites);
+  return true;
+}
+
+bool DebuggerMemory::CallData::drainAllocationsLog() {
+  Debugger* dbg = memory->getDebugger();
+
+  if (!dbg->trackingAllocationSites) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_TRACKING_ALLOCATIONS,
+                              "drainAllocationsLog");
+    return false;
+  }
+
+  size_t length = dbg->allocationsLog.length();
+
+  RootedArrayObject result(cx, NewDenseFullyAllocatedArray(cx, length));
+  if (!result) {
+    return false;
+  }
+  result->ensureDenseInitializedLength(0, length);
+
+  for (size_t i = 0; i < length; i++) {
+    RootedPlainObject obj(cx, NewBuiltinClassInstance<PlainObject>(cx));
+    if (!obj) {
+      return false;
+    }
+
+    // Don't pop the AllocationsLogEntry yet. The queue's links are followed
+    // by the GC to find the AllocationsLogEntry, but are not barriered, so
+    // we must edit them with great care. Use the queue entry in place, and
+    // then pop and delete together.
+    Debugger::AllocationsLogEntry& entry = dbg->allocationsLog.front();
+
+    RootedValue frame(cx, ObjectOrNullValue(entry.frame));
+    if (!DefineDataProperty(cx, obj, cx->names().frame, frame)) {
+      return false;
+    }
+
+    double when =
+        (entry.when - mozilla::TimeStamp::ProcessCreation()).ToMilliseconds();
+    RootedValue timestampValue(cx, NumberValue(when));
+    if (!DefineDataProperty(cx, obj, cx->names().timestamp, timestampValue)) {
+      return false;
+    }
+
+    RootedString className(
+        cx, Atomize(cx, entry.className, strlen(entry.className)));
+    if (!className) {
+      return false;
+    }
+    RootedValue classNameValue(cx, StringValue(className));
+    if (!DefineDataProperty(cx, obj, cx->names().class_, classNameValue)) {
+      return false;
+    }
+
+    RootedValue size(cx, NumberValue(entry.size));
+    if (!DefineDataProperty(cx, obj, cx->names().size, size)) {
+      return false;
+    }
+
+    RootedValue inNursery(cx, BooleanValue(entry.inNursery));
+    if (!DefineDataProperty(cx, obj, cx->names().inNursery, inNursery)) {
+      return false;
+    }
+
+    result->setDenseElement(i, ObjectValue(*obj));
+
+    // Pop the front queue entry, and delete it immediately, so that the GC
+    // sees the AllocationsLogEntry's HeapPtr barriers run atomically with
+    // the change to the graph (the queue link).
+    dbg->allocationsLog.popFront();
+  }
+
+  dbg->allocationsLogOverflowed = false;
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerMemory::CallData::getMaxAllocationsLogLength() {
+  args.rval().setInt32(memory->getDebugger()->maxAllocationsLogLength);
+  return true;
+}
+
+bool DebuggerMemory::CallData::setMaxAllocationsLogLength() {
+  if (!args.requireAtLeast(cx, "(set maxAllocationsLogLength)", 1)) {
+    return false;
+  }
+
+  int32_t max;
+  if (!ToInt32(cx, args[0], &max)) {
+    return false;
+  }
+
+  if (max < 1) {
+    JS_ReportErrorNumberASCII(
+        cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+        "(set maxAllocationsLogLength)'s parameter", "not a positive integer");
+    return false;
+  }
+
+  Debugger* dbg = memory->getDebugger();
+  dbg->maxAllocationsLogLength = max;
+
+  while (dbg->allocationsLog.length() > dbg->maxAllocationsLogLength) {
+    dbg->allocationsLog.popFront();
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerMemory::CallData::getAllocationSamplingProbability() {
+  args.rval().setDouble(memory->getDebugger()->allocationSamplingProbability);
+  return true;
+}
+
+bool DebuggerMemory::CallData::setAllocationSamplingProbability() {
+  if (!args.requireAtLeast(cx, "(set allocationSamplingProbability)", 1)) {
+    return false;
+  }
+
+  double probability;
+  if (!ToNumber(cx, args[0], &probability)) {
+    return false;
+  }
+
+  // Careful!  This must also reject NaN.
+  if (!(0.0 <= probability && probability <= 1.0)) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_UNEXPECTED_TYPE,
+                              "(set allocationSamplingProbability)'s parameter",
+                              "not a number between 0 and 1");
+    return false;
+  }
+
+  Debugger* dbg = memory->getDebugger();
+  if (dbg->allocationSamplingProbability != probability) {
+    dbg->allocationSamplingProbability = probability;
+
+    // If this is a change any debuggees would observe, have all debuggee
+    // realms recompute their sampling probabilities.
+    if (dbg->trackingAllocationSites) {
+      for (auto r = dbg->debuggees.all(); !r.empty(); r.popFront()) {
+        r.front()->realm()->chooseAllocationSamplingProbability();
+      }
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerMemory::CallData::getAllocationsLogOverflowed() {
+  args.rval().setBoolean(memory->getDebugger()->allocationsLogOverflowed);
+  return true;
+}
+
+bool DebuggerMemory::CallData::getOnGarbageCollection() {
+  return Debugger::getGarbageCollectionHook(cx, args, *memory->getDebugger());
+}
+
+bool DebuggerMemory::CallData::setOnGarbageCollection() {
+  return Debugger::setGarbageCollectionHook(cx, args, *memory->getDebugger());
+}
+
+/* Debugger.Memory.prototype.takeCensus */
+
+JS_PUBLIC_API void JS::dbg::SetDebuggerMallocSizeOf(
+    JSContext* cx, mozilla::MallocSizeOf mallocSizeOf) {
+  cx->runtime()->debuggerMallocSizeOf = mallocSizeOf;
+}
+
+JS_PUBLIC_API mozilla::MallocSizeOf JS::dbg::GetDebuggerMallocSizeOf(
+    JSContext* cx) {
+  return cx->runtime()->debuggerMallocSizeOf;
+}
+
+using JS::ubi::Census;
+using JS::ubi::CountBasePtr;
+using JS::ubi::CountTypePtr;
+
+// The takeCensus function works in three phases:
+//
+// 1) We examine the 'breakdown' property of our 'options' argument, and
+//    use that to build a CountType tree.
+//
+// 2) We create a count node for the root of our CountType tree, and then walk
+//    the heap, counting each node we find, expanding our tree of counts as we
+//    go.
+//
+// 3) We walk the tree of counts and produce JavaScript objects reporting the
+//    accumulated results.
+bool DebuggerMemory::CallData::takeCensus() {
+  Census census(cx);
+  CountTypePtr rootType;
+
+  RootedObject options(cx);
+  if (args.get(0).isObject()) {
+    options = &args[0].toObject();
+  }
+
+  if (!JS::ubi::ParseCensusOptions(cx, census, options, rootType)) {
+    return false;
+  }
+
+  JS::ubi::RootedCount rootCount(cx, rootType->makeCount());
+  if (!rootCount) {
+    return false;
+  }
+  JS::ubi::CensusHandler handler(census, rootCount,
+                                 cx->runtime()->debuggerMallocSizeOf);
+
+  Debugger* dbg = memory->getDebugger();
+  RootedObject dbgObj(cx, dbg->object);
+
+  // Populate our target set of debuggee zones.
+  for (WeakGlobalObjectSet::Range r = dbg->allDebuggees(); !r.empty();
+       r.popFront()) {
+    if (!census.targetZones.put(r.front()->zone())) {
+      return false;
+    }
+  }
+
+  {
+    Maybe<JS::AutoCheckCannotGC> maybeNoGC;
+    JS::ubi::RootList rootList(cx, maybeNoGC);
+    if (!rootList.init(dbgObj)) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+
+    JS::ubi::CensusTraversal traversal(cx, handler, maybeNoGC.ref());
+    traversal.wantNames = false;
+
+    if (!traversal.addStart(JS::ubi::Node(&rootList)) ||
+        !traversal.traverse()) {
+      ReportOutOfMemory(cx);
+      return false;
+    }
+  }
+
+  return handler.report(cx, args.rval());
+}
+
+/* Debugger.Memory property and method tables. */
+
+/* static */ const JSPropertySpec DebuggerMemory::properties[] = {
+    JS_DEBUG_PSGS("trackingAllocationSites", getTrackingAllocationSites,
+                  setTrackingAllocationSites),
+    JS_DEBUG_PSGS("maxAllocationsLogLength", getMaxAllocationsLogLength,
+                  setMaxAllocationsLogLength),
+    JS_DEBUG_PSGS("allocationSamplingProbability",
+                  getAllocationSamplingProbability,
+                  setAllocationSamplingProbability),
+    JS_DEBUG_PSG("allocationsLogOverflowed", getAllocationsLogOverflowed),
+    JS_DEBUG_PSGS("onGarbageCollection", getOnGarbageCollection,
+                  setOnGarbageCollection),
+    JS_PS_END};
+
+/* static */ const JSFunctionSpec DebuggerMemory::methods[] = {
+    JS_DEBUG_FN("drainAllocationsLog", drainAllocationsLog, 0),
+    JS_DEBUG_FN("takeCensus", takeCensus, 0), JS_FS_END};
diff --git a/js/src/debugger/DebuggerMemory.h b/js/src/debugger/DebuggerMemory.h
new file mode 100644
index 0000000000..29098a5adf
--- /dev/null
+++ b/js/src/debugger/DebuggerMemory.h
@@ -0,0 +1,41 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_DebuggerMemory_h
+#define debugger_DebuggerMemory_h
+
+#include "jsapi.h"
+
+#include "js/Class.h"
+#include "js/Value.h"
+#include "vm/JSContext.h"
+#include "vm/JSObject.h"
+
+namespace js {
+
+class DebuggerMemory : public NativeObject {
+  friend class Debugger;
+
+  static DebuggerMemory* checkThis(JSContext* cx, CallArgs& args);
+
+  Debugger* getDebugger();
+
+ public:
+  static DebuggerMemory* create(JSContext* cx, Debugger* dbg);
+
+  enum { JSSLOT_DEBUGGER, JSSLOT_COUNT };
+
+  static bool construct(JSContext* cx, unsigned argc, Value* vp);
+  static const JSClass class_;
+  static const JSPropertySpec properties[];
+  static const JSFunctionSpec methods[];
+
+  struct CallData;
+};
+
+} /* namespace js */
+
+#endif /* debugger_DebuggerMemory_h */
diff --git a/js/src/debugger/Environment-inl.h b/js/src/debugger/Environment-inl.h
new file mode 100644
index 0000000000..d297164b2d
--- /dev/null
+++ b/js/src/debugger/Environment-inl.h
@@ -0,0 +1,33 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Environment_inl_h
+#define debugger_Environment_inl_h
+
+#include "debugger/Environment.h"  // for DebuggerEnvironment
+
+#include "jstypes.h"            // for JS_PUBLIC_API
+#include "NamespaceImports.h"   // for Value
+#include "debugger/Debugger.h"  // for Debugger
+
+#include "debugger/Debugger-inl.h"  // for Debugger::fromJSObject
+
+class JS_PUBLIC_API JSObject;
+
+// The Debugger.Environment.prototype object also has a class of
+// DebuggerEnvironment::class_ so we differentiate instances from the prototype
+// based on the presence of an owner debugger.
+inline bool js::DebuggerEnvironment::isInstance() const {
+  return !getReservedSlot(OWNER_SLOT).isUndefined();
+}
+
+inline js::Debugger* js::DebuggerEnvironment::owner() const {
+  MOZ_ASSERT(isInstance());
+  JSObject* dbgobj = &getReservedSlot(OWNER_SLOT).toObject();
+  return Debugger::fromJSObject(dbgobj);
+}
+
+#endif /* debugger_Environment_inl_h */
diff --git a/js/src/debugger/Environment.cpp b/js/src/debugger/Environment.cpp
new file mode 100644
index 0000000000..e26ee79826
--- /dev/null
+++ b/js/src/debugger/Environment.cpp
@@ -0,0 +1,680 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Environment-inl.h"
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType
+#include "mozilla/Maybe.h"       // for Maybe, Some, Nothing
+#include "mozilla/Vector.h"      // for Vector
+
+#include <string.h>  // for strlen, size_t
+#include <utility>   // for move
+
+#include "jsapi.h"  // for Rooted, CallArgs, MutableHandle
+
+#include "debugger/Debugger.h"          // for Env, Debugger, ValueToIdentifier
+#include "debugger/Object.h"            // for DebuggerObject
+#include "debugger/Script.h"            // for DebuggerScript
+#include "frontend/BytecodeCompiler.h"  // for IsIdentifier
+#include "gc/Rooting.h"                 // for RootedDebuggerEnvironment
+#include "gc/Tracer.h"  // for TraceManuallyBarrieredCrossCompartmentEdge
+#include "js/friend/ErrorMessages.h"  // for GetErrorMessage, JSMSG_*
+#include "js/HeapAPI.h"               // for IsInsideNursery
+#include "vm/Compartment.h"           // for Compartment
+#include "vm/JSAtom.h"                // for Atomize, PinAtom
+#include "vm/JSContext.h"             // for JSContext
+#include "vm/JSFunction.h"            // for JSFunction
+#include "vm/JSObject.h"              // for JSObject, RequireObject
+#include "vm/NativeObject.h"          // for NativeObject, JSObject::is
+#include "vm/ObjectGroup.h"           // for GenericObject, NewObjectKind
+#include "vm/Realm.h"                 // for AutoRealm, ErrorCopier
+#include "vm/Scope.h"                 // for ScopeKind, ScopeKindString
+#include "vm/StringType.h"            // for JSAtom
+
+#include "vm/Compartment-inl.h"        // for Compartment::wrap
+#include "vm/EnvironmentObject-inl.h"  // for JSObject::enclosingEnvironment
+#include "vm/JSObject-inl.h"  // for IsInternalFunctionObject, NewObjectWithGivenProtoAndKind
+#include "vm/ObjectOperations-inl.h"  // for HasProperty, GetProperty
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+
+namespace js {
+class GlobalObject;
+}
+
+using namespace js;
+
+using js::frontend::IsIdentifier;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+
+const JSClassOps DebuggerEnvironment::classOps_ = {
+    nullptr,                               // addProperty
+    nullptr,                               // delProperty
+    nullptr,                               // enumerate
+    nullptr,                               // newEnumerate
+    nullptr,                               // resolve
+    nullptr,                               // mayResolve
+    nullptr,                               // finalize
+    nullptr,                               // call
+    nullptr,                               // hasInstance
+    nullptr,                               // construct
+    CallTraceMethod<DebuggerEnvironment>,  // trace
+};
+
+const JSClass DebuggerEnvironment::class_ = {
+    "Environment",
+    JSCLASS_HAS_PRIVATE |
+        JSCLASS_HAS_RESERVED_SLOTS(DebuggerEnvironment::RESERVED_SLOTS),
+    &classOps_};
+
+void DebuggerEnvironment::trace(JSTracer* trc) {
+  // There is a barrier on private pointers, so the Unbarriered marking
+  // is okay.
+  if (Env* referent = (JSObject*)getPrivate()) {
+    TraceManuallyBarrieredCrossCompartmentEdge(
+        trc, static_cast<JSObject*>(this), &referent,
+        "Debugger.Environment referent");
+    setPrivateUnbarriered(referent);
+  }
+}
+
+static DebuggerEnvironment* DebuggerEnvironment_checkThis(
+    JSContext* cx, const CallArgs& args) {
+  JSObject* thisobj = RequireObject(cx, args.thisv());
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerEnvironment>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Environment",
+                              "method", thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  // Forbid Debugger.Environment.prototype, which is of class
+  // DebuggerEnvironment::class_ but isn't a real working Debugger.Environment.
+  DebuggerEnvironment* nthisobj = &thisobj->as<DebuggerEnvironment>();
+  if (!nthisobj->isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Environment",
+                              "method", "prototype object");
+    return nullptr;
+  }
+
+  return nthisobj;
+}
+
+struct MOZ_STACK_CLASS DebuggerEnvironment::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  HandleDebuggerEnvironment environment;
+
+  CallData(JSContext* cx, const CallArgs& args, HandleDebuggerEnvironment env)
+      : cx(cx), args(args), environment(env) {}
+
+  bool typeGetter();
+  bool scopeKindGetter();
+  bool parentGetter();
+  bool objectGetter();
+  bool calleeScriptGetter();
+  bool inspectableGetter();
+  bool optimizedOutGetter();
+
+  bool namesMethod();
+  bool findMethod();
+  bool getVariableMethod();
+  bool setVariableMethod();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <DebuggerEnvironment::CallData::Method MyMethod>
+/* static */
+bool DebuggerEnvironment::CallData::ToNative(JSContext* cx, unsigned argc,
+                                             Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedDebuggerEnvironment environment(
+      cx, DebuggerEnvironment_checkThis(cx, args));
+  if (!environment) {
+    return false;
+  }
+
+  CallData data(cx, args, environment);
+  return (data.*MyMethod)();
+}
+
+/* static */
+bool DebuggerEnvironment::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Environment");
+  return false;
+}
+
+static bool IsDeclarative(Env* env) {
+  return env->is<DebugEnvironmentProxy>() &&
+         env->as<DebugEnvironmentProxy>().isForDeclarative();
+}
+
+template <typename T>
+static bool IsDebugEnvironmentWrapper(Env* env) {
+  return env->is<DebugEnvironmentProxy>() &&
+         env->as<DebugEnvironmentProxy>().environment().is<T>();
+}
+
+bool DebuggerEnvironment::CallData::typeGetter() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  DebuggerEnvironmentType type = environment->type();
+
+  const char* s;
+  switch (type) {
+    case DebuggerEnvironmentType::Declarative:
+      s = "declarative";
+      break;
+    case DebuggerEnvironmentType::With:
+      s = "with";
+      break;
+    case DebuggerEnvironmentType::Object:
+      s = "object";
+      break;
+  }
+
+  JSAtom* str = Atomize(cx, s, strlen(s), PinAtom);
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::scopeKindGetter() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  Maybe<ScopeKind> kind = environment->scopeKind();
+  if (kind.isSome()) {
+    const char* s = ScopeKindString(*kind);
+    JSAtom* str = Atomize(cx, s, strlen(s), PinAtom);
+    if (!str) {
+      return false;
+    }
+    args.rval().setString(str);
+  } else {
+    args.rval().setNull();
+  }
+
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::parentGetter() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  RootedDebuggerEnvironment result(cx);
+  if (!environment->getParent(cx, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::objectGetter() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  if (environment->type() == DebuggerEnvironmentType::Declarative) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_NO_ENV_OBJECT);
+    return false;
+  }
+
+  RootedDebuggerObject result(cx);
+  if (!environment->getObject(cx, &result)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::calleeScriptGetter() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  RootedDebuggerScript result(cx);
+  if (!environment->getCalleeScript(cx, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::inspectableGetter() {
+  args.rval().setBoolean(environment->isDebuggee());
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::optimizedOutGetter() {
+  args.rval().setBoolean(environment->isOptimized());
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::namesMethod() {
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  Rooted<IdVector> ids(cx, IdVector(cx));
+  if (!DebuggerEnvironment::getNames(cx, environment, &ids)) {
+    return false;
+  }
+
+  RootedObject obj(cx, IdVectorToArray(cx, ids));
+  if (!obj) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::findMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Environment.find", 1)) {
+    return false;
+  }
+
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  if (!ValueToIdentifier(cx, args[0], &id)) {
+    return false;
+  }
+
+  RootedDebuggerEnvironment result(cx);
+  if (!DebuggerEnvironment::find(cx, environment, id, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerEnvironment::CallData::getVariableMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Environment.getVariable", 1)) {
+    return false;
+  }
+
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  if (!ValueToIdentifier(cx, args[0], &id)) {
+    return false;
+  }
+
+  return DebuggerEnvironment::getVariable(cx, environment, id, args.rval());
+}
+
+bool DebuggerEnvironment::CallData::setVariableMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Environment.setVariable", 2)) {
+    return false;
+  }
+
+  if (!environment->requireDebuggee(cx)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  if (!ValueToIdentifier(cx, args[0], &id)) {
+    return false;
+  }
+
+  if (!DebuggerEnvironment::setVariable(cx, environment, id, args[1])) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerEnvironment::requireDebuggee(JSContext* cx) const {
+  if (!isDebuggee()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_NOT_DEBUGGEE, "Debugger.Environment",
+                              "environment");
+
+    return false;
+  }
+
+  return true;
+}
+
+const JSPropertySpec DebuggerEnvironment::properties_[] = {
+    JS_DEBUG_PSG("type", typeGetter),
+    JS_DEBUG_PSG("scopeKind", scopeKindGetter),
+    JS_DEBUG_PSG("parent", parentGetter),
+    JS_DEBUG_PSG("object", objectGetter),
+    JS_DEBUG_PSG("calleeScript", calleeScriptGetter),
+    JS_DEBUG_PSG("inspectable", inspectableGetter),
+    JS_DEBUG_PSG("optimizedOut", optimizedOutGetter),
+    JS_PS_END};
+
+const JSFunctionSpec DebuggerEnvironment::methods_[] = {
+    JS_DEBUG_FN("names", namesMethod, 0), JS_DEBUG_FN("find", findMethod, 1),
+    JS_DEBUG_FN("getVariable", getVariableMethod, 1),
+    JS_DEBUG_FN("setVariable", setVariableMethod, 2), JS_FS_END};
+
+/* static */
+NativeObject* DebuggerEnvironment::initClass(JSContext* cx,
+                                             Handle<GlobalObject*> global,
+                                             HandleObject dbgCtor) {
+  return InitClass(cx, dbgCtor, nullptr, &DebuggerEnvironment::class_,
+                   construct, 0, properties_, methods_, nullptr, nullptr);
+}
+
+/* static */
+DebuggerEnvironment* DebuggerEnvironment::create(JSContext* cx,
+                                                 HandleObject proto,
+                                                 HandleObject referent,
+                                                 HandleNativeObject debugger) {
+  DebuggerEnvironment* obj =
+      IsInsideNursery(referent)
+          ? NewObjectWithGivenProto<DebuggerEnvironment>(cx, proto)
+          : NewTenuredObjectWithGivenProto<DebuggerEnvironment>(cx, proto);
+  if (!obj) {
+    return nullptr;
+  }
+
+  obj->setPrivateGCThing(referent);
+  obj->setReservedSlot(OWNER_SLOT, ObjectValue(*debugger));
+
+  return obj;
+}
+
+/* static */
+DebuggerEnvironmentType DebuggerEnvironment::type() const {
+  // Don't bother switching compartments just to check env's type.
+  if (IsDeclarative(referent())) {
+    return DebuggerEnvironmentType::Declarative;
+  }
+  if (IsDebugEnvironmentWrapper<WithEnvironmentObject>(referent())) {
+    return DebuggerEnvironmentType::With;
+  }
+  return DebuggerEnvironmentType::Object;
+}
+
+mozilla::Maybe<ScopeKind> DebuggerEnvironment::scopeKind() const {
+  if (!referent()->is<DebugEnvironmentProxy>()) {
+    return Nothing();
+  }
+  EnvironmentObject& env =
+      referent()->as<DebugEnvironmentProxy>().environment();
+  Scope* scope = GetEnvironmentScope(env);
+  return scope ? Some(scope->kind()) : Nothing();
+}
+
+bool DebuggerEnvironment::getParent(
+    JSContext* cx, MutableHandleDebuggerEnvironment result) const {
+  // Don't bother switching compartments just to get env's parent.
+  Rooted<Env*> parent(cx, referent()->enclosingEnvironment());
+  if (!parent) {
+    result.set(nullptr);
+    return true;
+  }
+
+  return owner()->wrapEnvironment(cx, parent, result);
+}
+
+bool DebuggerEnvironment::getObject(JSContext* cx,
+                                    MutableHandleDebuggerObject result) const {
+  MOZ_ASSERT(type() != DebuggerEnvironmentType::Declarative);
+
+  // Don't bother switching compartments just to get env's object.
+  RootedObject object(cx);
+  if (IsDebugEnvironmentWrapper<WithEnvironmentObject>(referent())) {
+    object.set(&referent()
+                    ->as<DebugEnvironmentProxy>()
+                    .environment()
+                    .as<WithEnvironmentObject>()
+                    .object());
+  } else if (IsDebugEnvironmentWrapper<NonSyntacticVariablesObject>(
+                 referent())) {
+    object.set(&referent()
+                    ->as<DebugEnvironmentProxy>()
+                    .environment()
+                    .as<NonSyntacticVariablesObject>());
+  } else {
+    object.set(referent());
+    MOZ_ASSERT(!object->is<DebugEnvironmentProxy>());
+  }
+
+  return owner()->wrapDebuggeeObject(cx, object, result);
+}
+
+bool DebuggerEnvironment::getCalleeScript(
+    JSContext* cx, MutableHandleDebuggerScript result) const {
+  if (!referent()->is<DebugEnvironmentProxy>()) {
+    result.set(nullptr);
+    return true;
+  }
+
+  JSObject& scope = referent()->as<DebugEnvironmentProxy>().environment();
+  if (!scope.is<CallObject>()) {
+    result.set(nullptr);
+    return true;
+  }
+
+  Rooted<BaseScript*> script(cx, scope.as<CallObject>().callee().baseScript());
+
+  DebuggerScript* scriptObject = owner()->wrapScript(cx, script);
+  if (!scriptObject) {
+    return false;
+  }
+
+  result.set(scriptObject);
+  return true;
+}
+
+bool DebuggerEnvironment::isDebuggee() const {
+  MOZ_ASSERT(referent());
+  MOZ_ASSERT(!referent()->is<EnvironmentObject>());
+
+  return owner()->observesGlobal(&referent()->nonCCWGlobal());
+}
+
+bool DebuggerEnvironment::isOptimized() const {
+  return referent()->is<DebugEnvironmentProxy>() &&
+         referent()->as<DebugEnvironmentProxy>().isOptimizedOut();
+}
+
+/* static */
+bool DebuggerEnvironment::getNames(JSContext* cx,
+                                   HandleDebuggerEnvironment environment,
+                                   MutableHandle<IdVector> result) {
+  MOZ_ASSERT(environment->isDebuggee());
+
+  Rooted<Env*> referent(cx, environment->referent());
+
+  RootedIdVector ids(cx);
+  {
+    Maybe<AutoRealm> ar;
+    ar.emplace(cx, referent);
+
+    ErrorCopier ec(ar);
+    if (!GetPropertyKeys(cx, referent, JSITER_HIDDEN, &ids)) {
+      return false;
+    }
+  }
+
+  for (size_t i = 0; i < ids.length(); ++i) {
+    jsid id = ids[i];
+    if (JSID_IS_ATOM(id) && IsIdentifier(JSID_TO_ATOM(id))) {
+      cx->markId(id);
+      if (!result.append(id)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+/* static */
+bool DebuggerEnvironment::find(JSContext* cx,
+                               HandleDebuggerEnvironment environment,
+                               HandleId id,
+                               MutableHandleDebuggerEnvironment result) {
+  MOZ_ASSERT(environment->isDebuggee());
+
+  Rooted<Env*> env(cx, environment->referent());
+  Debugger* dbg = environment->owner();
+
+  {
+    Maybe<AutoRealm> ar;
+    ar.emplace(cx, env);
+
+    cx->markId(id);
+
+    // This can trigger resolve hooks.
+    ErrorCopier ec(ar);
+    for (; env; env = env->enclosingEnvironment()) {
+      bool found;
+      if (!HasProperty(cx, env, id, &found)) {
+        return false;
+      }
+      if (found) {
+        break;
+      }
+    }
+  }
+
+  if (!env) {
+    result.set(nullptr);
+    return true;
+  }
+
+  return dbg->wrapEnvironment(cx, env, result);
+}
+
+/* static */
+bool DebuggerEnvironment::getVariable(JSContext* cx,
+                                      HandleDebuggerEnvironment environment,
+                                      HandleId id, MutableHandleValue result) {
+  MOZ_ASSERT(environment->isDebuggee());
+
+  Rooted<Env*> referent(cx, environment->referent());
+  Debugger* dbg = environment->owner();
+
+  {
+    Maybe<AutoRealm> ar;
+    ar.emplace(cx, referent);
+
+    cx->markId(id);
+
+    // This can trigger getters.
+    ErrorCopier ec(ar);
+
+    bool found;
+    if (!HasProperty(cx, referent, id, &found)) {
+      return false;
+    }
+    if (!found) {
+      result.setUndefined();
+      return true;
+    }
+
+    // For DebugEnvironmentProxys, we get sentinel values for optimized out
+    // slots and arguments instead of throwing (the default behavior).
+    //
+    // See wrapDebuggeeValue for how the sentinel values are wrapped.
+    if (referent->is<DebugEnvironmentProxy>()) {
+      Rooted<DebugEnvironmentProxy*> env(
+          cx, &referent->as<DebugEnvironmentProxy>());
+      if (!DebugEnvironmentProxy::getMaybeSentinelValue(cx, env, id, result)) {
+        return false;
+      }
+    } else {
+      if (!GetProperty(cx, referent, referent, id, result)) {
+        return false;
+      }
+    }
+  }
+
+  // When we've faked up scope chain objects for optimized-out scopes,
+  // declarative environments may contain internal JSFunction objects, which
+  // we shouldn't expose to the user.
+  if (result.isObject()) {
+    RootedObject obj(cx, &result.toObject());
+    if (obj->is<JSFunction>() &&
+        IsInternalFunctionObject(obj->as<JSFunction>()))
+      result.setMagic(JS_OPTIMIZED_OUT);
+  }
+
+  return dbg->wrapDebuggeeValue(cx, result);
+}
+
+/* static */
+bool DebuggerEnvironment::setVariable(JSContext* cx,
+                                      HandleDebuggerEnvironment environment,
+                                      HandleId id, HandleValue value_) {
+  MOZ_ASSERT(environment->isDebuggee());
+
+  Rooted<Env*> referent(cx, environment->referent());
+  Debugger* dbg = environment->owner();
+
+  RootedValue value(cx, value_);
+  if (!dbg->unwrapDebuggeeValue(cx, &value)) {
+    return false;
+  }
+
+  {
+    Maybe<AutoRealm> ar;
+    ar.emplace(cx, referent);
+    if (!cx->compartment()->wrap(cx, &value)) {
+      return false;
+    }
+    cx->markId(id);
+
+    // This can trigger setters.
+    ErrorCopier ec(ar);
+
+    // Make sure the environment actually has the specified binding.
+    bool found;
+    if (!HasProperty(cx, referent, id, &found)) {
+      return false;
+    }
+    if (!found) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_VARIABLE_NOT_FOUND);
+      return false;
+    }
+
+    // Just set the property.
+    if (!SetProperty(cx, referent, id, value)) {
+      return false;
+    }
+  }
+
+  return true;
+}
diff --git a/js/src/debugger/Environment.h b/js/src/debugger/Environment.h
new file mode 100644
index 0000000000..0a02a25ed2
--- /dev/null
+++ b/js/src/debugger/Environment.h
@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Environment_h
+#define debugger_Environment_h
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+#include "mozilla/Attributes.h"  // for MOZ_MUST_USE
+#include "mozilla/Maybe.h"       // for Maybe
+
+#include "jstypes.h"            // for JS_PUBLIC_API
+#include "NamespaceImports.h"   // for Value, HandleId, HandleObject
+#include "debugger/Debugger.h"  // for Env
+#include "gc/Rooting.h"         // for HandleDebuggerEnvironment
+#include "js/PropertySpec.h"    // for JSFunctionSpec, JSPropertySpec
+#include "js/RootingAPI.h"      // for Handle, MutableHandle
+#include "vm/NativeObject.h"    // for NativeObject
+#include "vm/Scope.h"           // for ScopeKind
+
+class JS_PUBLIC_API JSObject;
+struct JS_PUBLIC_API JSContext;
+class JSTracer;
+
+namespace js {
+
+class GlobalObject;
+
+enum class DebuggerEnvironmentType { Declarative, With, Object };
+
+class DebuggerEnvironment : public NativeObject {
+ public:
+  enum { OWNER_SLOT };
+
+  static const unsigned RESERVED_SLOTS = 1;
+
+  static const JSClass class_;
+
+  static NativeObject* initClass(JSContext* cx, Handle<GlobalObject*> global,
+                                 HandleObject dbgCtor);
+  static DebuggerEnvironment* create(JSContext* cx, HandleObject proto,
+                                     HandleObject referent,
+                                     HandleNativeObject debugger);
+
+  void trace(JSTracer* trc);
+
+  DebuggerEnvironmentType type() const;
+  mozilla::Maybe<ScopeKind> scopeKind() const;
+  MOZ_MUST_USE bool getParent(JSContext* cx,
+                              MutableHandleDebuggerEnvironment result) const;
+  MOZ_MUST_USE bool getObject(JSContext* cx,
+                              MutableHandleDebuggerObject result) const;
+  MOZ_MUST_USE bool getCalleeScript(JSContext* cx,
+                                    MutableHandleDebuggerScript result) const;
+  bool isDebuggee() const;
+  bool isOptimized() const;
+
+  static MOZ_MUST_USE bool getNames(JSContext* cx,
+                                    HandleDebuggerEnvironment environment,
+                                    MutableHandle<IdVector> result);
+  static MOZ_MUST_USE bool find(JSContext* cx,
+                                HandleDebuggerEnvironment environment,
+                                HandleId id,
+                                MutableHandleDebuggerEnvironment result);
+  static MOZ_MUST_USE bool getVariable(JSContext* cx,
+                                       HandleDebuggerEnvironment environment,
+                                       HandleId id, MutableHandleValue result);
+  static MOZ_MUST_USE bool setVariable(JSContext* cx,
+                                       HandleDebuggerEnvironment environment,
+                                       HandleId id, HandleValue value);
+
+  bool isInstance() const;
+  Debugger* owner() const;
+
+  Env* referent() const {
+    Env* env = static_cast<Env*>(getPrivate());
+    MOZ_ASSERT(env);
+    return env;
+  }
+
+ private:
+  static const JSClassOps classOps_;
+
+  static const JSPropertySpec properties_[];
+  static const JSFunctionSpec methods_[];
+
+  bool requireDebuggee(JSContext* cx) const;
+
+  static MOZ_MUST_USE bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+};
+
+} /* namespace js */
+
+#endif /* debugger_Environment_h */
diff --git a/js/src/debugger/Frame-inl.h b/js/src/debugger/Frame-inl.h
new file mode 100644
index 0000000000..6cb595d44c
--- /dev/null
+++ b/js/src/debugger/Frame-inl.h
@@ -0,0 +1,27 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Frame_inl_h
+#define debugger_Frame_inl_h
+
+#include "debugger/Frame.h"  // for DebuggerFrame
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+
+#include "NamespaceImports.h"  // for Value
+
+inline bool js::DebuggerFrame::hasGeneratorInfo() const {
+  return !getReservedSlot(GENERATOR_INFO_SLOT).isUndefined();
+}
+
+inline js::DebuggerFrame::GeneratorInfo* js::DebuggerFrame::generatorInfo()
+    const {
+  MOZ_ASSERT(hasGeneratorInfo());
+  return static_cast<GeneratorInfo*>(
+      getReservedSlot(GENERATOR_INFO_SLOT).toPrivate());
+}
+
+#endif /* debugger_Frame_inl_h */
diff --git a/js/src/debugger/Frame.cpp b/js/src/debugger/Frame.cpp
new file mode 100644
index 0000000000..89c9254c98
--- /dev/null
+++ b/js/src/debugger/Frame.cpp
@@ -0,0 +1,1942 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Frame-inl.h"
+
+#include "mozilla/Assertions.h"   // for AssertionConditionType
+#include "mozilla/HashTable.h"    // for HashMapEntry
+#include "mozilla/Maybe.h"        // for Maybe
+#include "mozilla/Range.h"        // for Range
+#include "mozilla/RangedPtr.h"    // for RangedPtr
+#include "mozilla/Result.h"       // for Result
+#include "mozilla/ScopeExit.h"    // for MakeScopeExit, ScopeExit
+#include "mozilla/ThreadLocal.h"  // for ThreadLocal
+#include "mozilla/Vector.h"       // for Vector
+
+#include <stddef.h>  // for size_t
+#include <stdint.h>  // for int32_t
+#include <string.h>  // for strlen
+#include <utility>   // for std::move
+
+#include "jsapi.h"  // for CallArgs, Handle
+#include "jsnum.h"  // for Int32ToString
+
+#include "builtin/Array.h"      // for NewDenseCopiedArray
+#include "debugger/Debugger.h"  // for Completion, Debugger
+#include "debugger/DebugScript.h"
+#include "debugger/Environment.h"          // for DebuggerEnvironment
+#include "debugger/NoExecute.h"            // for LeaveDebuggeeNoExecute
+#include "debugger/Object.h"               // for DebuggerObject
+#include "debugger/Script.h"               // for DebuggerScript
+#include "frontend/BytecodeCompilation.h"  // for CompileEvalScript
+#include "frontend/SharedContext.h"        // for GlobalScharedContext
+#include "gc/Barrier.h"                    // for HeapPtr
+#include "gc/FreeOp.h"                     // for JSFreeOp
+#include "gc/GC.h"                         // for MemoryUse
+#include "gc/Marking.h"                    // for IsAboutToBeFinalized
+#include "gc/Rooting.h"                    // for RootedDebuggerFrame
+#include "gc/Tracer.h"                     // for TraceCrossCompartmentEdge
+#include "gc/ZoneAllocator.h"              // for AddCellMemory
+#include "jit/JSJitFrameIter.h"            // for InlineFrameIterator
+#include "jit/RematerializedFrame.h"       // for RematerializedFrame
+#include "js/friend/ErrorMessages.h"       // for GetErrorMessage, JSMSG_*
+#include "js/Object.h"                     // for SetReservedSlot
+#include "js/Proxy.h"                      // for PrivateValue
+#include "js/SourceText.h"                 // for SourceText, SourceOwnership
+#include "js/StableStringChars.h"          // for AutoStableStringChars
+#include "vm/ArgumentsObject.h"            // for ArgumentsObject
+#include "vm/ArrayObject.h"                // for ArrayObject
+#include "vm/AsyncFunction.h"              // for AsyncFunctionGeneratorObject
+#include "vm/AsyncIteration.h"             // for AsyncGeneratorObject
+#include "vm/BytecodeUtil.h"               // for JSDVG_SEARCH_STACK
+#include "vm/Compartment.h"                // for Compartment
+#include "vm/EnvironmentObject.h"          // for IsGlobalLexicalEnvironment
+#include "vm/GeneratorObject.h"            // for AbstractGeneratorObject
+#include "vm/GlobalObject.h"               // for GlobalObject
+#include "vm/Interpreter.h"                // for Call, ExecuteKernel
+#include "vm/JSAtom.h"                     // for Atomize
+#include "vm/JSContext.h"                  // for JSContext, ReportValueError
+#include "vm/JSFunction.h"                 // for JSFunction, NewNativeFunction
+#include "vm/JSObject.h"                   // for JSObject, RequireObject
+#include "vm/JSScript.h"                   // for JSScript
+#include "vm/NativeObject.h"               // for NativeDefineDataProperty
+#include "vm/Realm.h"                      // for AutoRealm
+#include "vm/Runtime.h"                    // for JSAtomState
+#include "vm/Scope.h"                      // for PositionalFormalParameterIter
+#include "vm/Stack.h"                      // for AbstractFramePtr, FrameIter
+#include "vm/StringType.h"                 // for PropertyName, JSString
+#include "wasm/WasmDebug.h"                // for DebugState
+#include "wasm/WasmInstance.h"             // for Instance
+#include "wasm/WasmJS.h"                   // for WasmInstanceObject
+#include "wasm/WasmTypes.h"                // for DebugFrame
+
+#include "debugger/Debugger-inl.h"  // for Debugger::fromJSObject
+#include "gc/WeakMap-inl.h"         // for WeakMap::remove
+#include "vm/Compartment-inl.h"     // for Compartment::wrap
+#include "vm/JSContext-inl.h"       // for JSContext::check
+#include "vm/JSObject-inl.h"        // for NewObjectWithGivenProto
+#include "vm/JSScript-inl.h"        // for JSScript::ensureHasAnalyzedArgsUsage
+#include "vm/NativeObject-inl.h"    // for NativeObject::global
+#include "vm/ObjectOperations-inl.h"  // for GetProperty
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+#include "vm/Stack-inl.h"             // for AbstractFramePtr::script
+
+namespace js {
+namespace jit {
+class JitFrameLayout;
+} /* namespace jit */
+} /* namespace js */
+
+using namespace js;
+
+using JS::AutoStableStringChars;
+using JS::CompileOptions;
+using JS::SourceOwnership;
+using JS::SourceText;
+using mozilla::MakeScopeExit;
+using mozilla::Maybe;
+
+ScriptedOnStepHandler::ScriptedOnStepHandler(JSObject* object)
+    : object_(object) {
+  MOZ_ASSERT(object_->isCallable());
+}
+
+JSObject* ScriptedOnStepHandler::object() const { return object_; }
+
+void ScriptedOnStepHandler::hold(JSObject* owner) {
+  AddCellMemory(owner, allocSize(), MemoryUse::DebuggerOnStepHandler);
+}
+
+void ScriptedOnStepHandler::drop(JSFreeOp* fop, JSObject* owner) {
+  fop->delete_(owner, this, allocSize(), MemoryUse::DebuggerOnStepHandler);
+}
+
+void ScriptedOnStepHandler::trace(JSTracer* tracer) {
+  TraceEdge(tracer, &object_, "OnStepHandlerFunction.object");
+}
+
+bool ScriptedOnStepHandler::onStep(JSContext* cx, HandleDebuggerFrame frame,
+                                   ResumeMode& resumeMode,
+                                   MutableHandleValue vp) {
+  RootedValue fval(cx, ObjectValue(*object_));
+  RootedValue rval(cx);
+  if (!js::Call(cx, fval, frame, &rval)) {
+    return false;
+  }
+
+  return ParseResumptionValue(cx, rval, resumeMode, vp);
+};
+
+size_t ScriptedOnStepHandler::allocSize() const { return sizeof(*this); }
+
+ScriptedOnPopHandler::ScriptedOnPopHandler(JSObject* object) : object_(object) {
+  MOZ_ASSERT(object->isCallable());
+}
+
+JSObject* ScriptedOnPopHandler::object() const { return object_; }
+
+void ScriptedOnPopHandler::hold(JSObject* owner) {
+  AddCellMemory(owner, allocSize(), MemoryUse::DebuggerOnPopHandler);
+}
+
+void ScriptedOnPopHandler::drop(JSFreeOp* fop, JSObject* owner) {
+  fop->delete_(owner, this, allocSize(), MemoryUse::DebuggerOnPopHandler);
+}
+
+void ScriptedOnPopHandler::trace(JSTracer* tracer) {
+  TraceEdge(tracer, &object_, "OnStepHandlerFunction.object");
+}
+
+bool ScriptedOnPopHandler::onPop(JSContext* cx, HandleDebuggerFrame frame,
+                                 const Completion& completion,
+                                 ResumeMode& resumeMode,
+                                 MutableHandleValue vp) {
+  Debugger* dbg = frame->owner();
+
+  RootedValue completionValue(cx);
+  if (!completion.buildCompletionValue(cx, dbg, &completionValue)) {
+    return false;
+  }
+
+  RootedValue fval(cx, ObjectValue(*object_));
+  RootedValue rval(cx);
+  if (!js::Call(cx, fval, frame, completionValue, &rval)) {
+    return false;
+  }
+
+  return ParseResumptionValue(cx, rval, resumeMode, vp);
+};
+
+size_t ScriptedOnPopHandler::allocSize() const { return sizeof(*this); }
+
+// The Debugger.Frame.prototype object also has a class of
+// DebuggerFrame::class_ so we differentiate instances from the prototype
+// based on the presence of an owner debugger.
+bool js::DebuggerFrame::isInstance() const {
+  return !getReservedSlot(OWNER_SLOT).isUndefined();
+}
+js::Debugger* js::DebuggerFrame::owner() const {
+  MOZ_ASSERT(isInstance());
+  JSObject* dbgobj = &getReservedSlot(OWNER_SLOT).toObject();
+  return Debugger::fromJSObject(dbgobj);
+}
+
+const JSClassOps DebuggerFrame::classOps_ = {
+    nullptr,                         // addProperty
+    nullptr,                         // delProperty
+    nullptr,                         // enumerate
+    nullptr,                         // newEnumerate
+    nullptr,                         // resolve
+    nullptr,                         // mayResolve
+    finalize,                        // finalize
+    nullptr,                         // call
+    nullptr,                         // hasInstance
+    nullptr,                         // construct
+    CallTraceMethod<DebuggerFrame>,  // trace
+};
+
+const JSClass DebuggerFrame::class_ = {
+    "Frame",
+    JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS) |
+        // We require foreground finalization so we can destruct GeneratorInfo's
+        // HeapPtrs.
+        JSCLASS_FOREGROUND_FINALIZE,
+    &DebuggerFrame::classOps_};
+
+enum { JSSLOT_DEBUGARGUMENTS_FRAME, JSSLOT_DEBUGARGUMENTS_COUNT };
+
+const JSClass DebuggerArguments::class_ = {
+    "Arguments", JSCLASS_HAS_RESERVED_SLOTS(JSSLOT_DEBUGARGUMENTS_COUNT)};
+
+bool DebuggerFrame::resume(const FrameIter& iter) {
+  FrameIter::Data* data = iter.copyData();
+  if (!data) {
+    return false;
+  }
+  setFrameIterData(data);
+  return true;
+}
+
+bool DebuggerFrame::hasAnyHooks() const {
+  return !getReservedSlot(ONSTEP_HANDLER_SLOT).isUndefined() ||
+         !getReservedSlot(ONPOP_HANDLER_SLOT).isUndefined();
+}
+
+/* static */
+NativeObject* DebuggerFrame::initClass(JSContext* cx,
+                                       Handle<GlobalObject*> global,
+                                       HandleObject dbgCtor) {
+  return InitClass(cx, dbgCtor, nullptr, &class_, construct, 0, properties_,
+                   methods_, nullptr, nullptr);
+}
+
+/* static */
+DebuggerFrame* DebuggerFrame::create(
+    JSContext* cx, HandleObject proto, HandleNativeObject debugger,
+    const FrameIter* maybeIter,
+    Handle<AbstractGeneratorObject*> maybeGenerator) {
+  DebuggerFrame* frame = NewObjectWithGivenProto<DebuggerFrame>(cx, proto);
+  if (!frame) {
+    return nullptr;
+  }
+
+  frame->setReservedSlot(OWNER_SLOT, ObjectValue(*debugger));
+
+  if (maybeIter) {
+    FrameIter::Data* data = maybeIter->copyData();
+    if (!data) {
+      return nullptr;
+    }
+
+    frame->setFrameIterData(data);
+  }
+
+  if (maybeGenerator) {
+    if (!frame->setGeneratorInfo(cx, maybeGenerator)) {
+      frame->freeFrameIterData(cx->runtime()->defaultFreeOp());
+      return nullptr;
+    }
+  }
+
+  return frame;
+}
+
+/**
+ * Information held by a DebuggerFrame about a generator/async call. A
+ * Debugger.Frame's GENERATOR_INFO_SLOT, if set, holds a PrivateValue pointing
+ * to one of these.
+ *
+ * This is created and attached as soon as a generator object is created for a
+ * debuggee generator/async frame, retained across suspensions and resumptions,
+ * and cleared when the generator call ends permanently.
+ *
+ * It may seem like this information might belong in ordinary reserved slots on
+ * the DebuggerFrame object. But that isn't possible:
+ *
+ * 1) Slots cannot contain cross-compartment references directly.
+ * 2) Ordinary cross-compartment wrappers aren't good enough, because the
+ *    debugger must create its own magic entries in the wrapper table for the GC
+ *    to get zone collection groups right.
+ * 3) Even if we make debugger wrapper table entries by hand, hiding
+ *    cross-compartment edges as PrivateValues doesn't call post-barriers, and
+ *    the generational GC won't update our pointer when the generator object
+ *    gets tenured.
+ *
+ * Yes, officer, I definitely knew all this in advance and designed it this way
+ * the first time.
+ *
+ * Note that it is not necessary to have a second cross-compartment wrapper
+ * table entry to cover the pointer to the generator's script. The wrapper table
+ * entries play two roles: they help the GC put a debugger zone in the same zone
+ * group as its debuggee, and they serve as roots when collecting the debuggee
+ * zone, but not the debugger zone. Since an AbstractGeneratorObject holds a
+ * strong reference to its callee's script (via the callee), and the AGO and the
+ * script are always in the same compartment, it suffices to add a
+ * cross-compartment wrapper table entry for the Debugger.Frame -> AGO edge.
+ */
+class DebuggerFrame::GeneratorInfo {
+  // An unwrapped cross-compartment reference to the generator object.
+  //
+  // Always an object.
+  //
+  // This cannot be GCPtr because we are not always destructed during sweeping;
+  // a Debugger.Frame's generator is also cleared when the generator returns
+  // permanently.
+  const HeapPtr<Value> unwrappedGenerator_;
+
+  // A cross-compartment reference to the generator's script.
+  const HeapPtr<JSScript*> generatorScript_;
+
+ public:
+  GeneratorInfo(Handle<AbstractGeneratorObject*> unwrappedGenerator,
+                HandleScript generatorScript)
+      : unwrappedGenerator_(ObjectValue(*unwrappedGenerator)),
+        generatorScript_(generatorScript) {}
+
+  void trace(JSTracer* tracer, DebuggerFrame& frameObj) {
+    TraceCrossCompartmentEdge(tracer, &frameObj, &unwrappedGenerator_,
+                              "Debugger.Frame generator object");
+    TraceCrossCompartmentEdge(tracer, &frameObj, &generatorScript_,
+                              "Debugger.Frame generator script");
+  }
+
+  AbstractGeneratorObject& unwrappedGenerator() const {
+    return unwrappedGenerator_.toObject().as<AbstractGeneratorObject>();
+  }
+
+  JSScript* generatorScript() { return generatorScript_; }
+
+  bool isGeneratorScriptAboutToBeFinalized() {
+    return IsAboutToBeFinalized(&generatorScript_);
+  }
+};
+
+bool js::DebuggerFrame::isSuspended() const {
+  return hasGeneratorInfo() &&
+         generatorInfo()->unwrappedGenerator().isSuspended();
+}
+
+js::AbstractGeneratorObject& js::DebuggerFrame::unwrappedGenerator() const {
+  return generatorInfo()->unwrappedGenerator();
+}
+
+#ifdef DEBUG
+JSScript* js::DebuggerFrame::generatorScript() const {
+  return generatorInfo()->generatorScript();
+}
+#endif
+
+bool DebuggerFrame::setGeneratorInfo(JSContext* cx,
+                                     Handle<AbstractGeneratorObject*> genObj) {
+  cx->check(this);
+
+  MOZ_ASSERT(!hasGeneratorInfo());
+  MOZ_ASSERT(!genObj->isClosed());
+
+  // When we initialize the generator information, we do not need to adjust
+  // the stepper increment, because either it was already incremented when
+  // the step hook was added, or we're setting this into on a new DebuggerFrame
+  // that has not yet had the chance for a hook to be added to it.
+  MOZ_ASSERT_IF(onStepHandler(), frameIterData());
+  MOZ_ASSERT_IF(!frameIterData(), !onStepHandler());
+
+  // There are two relations we must establish:
+  //
+  // 1) The DebuggerFrame must point to the AbstractGeneratorObject.
+  //
+  // 2) The generator's script's observer count must be bumped.
+
+  RootedScript script(cx, genObj->callee().nonLazyScript());
+  auto info = cx->make_unique<GeneratorInfo>(genObj, script);
+  if (!info) {
+    return false;
+  }
+
+  AutoRealm ar(cx, script);
+
+  // All frames running a debuggee script must themselves be marked as
+  // debuggee frames. Bumping a script's generator observer count makes it a
+  // debuggee, so we need to mark all frames on the stack running it as
+  // debuggees as well, not just this one. This call takes care of all that.
+  if (!Debugger::ensureExecutionObservabilityOfScript(cx, script)) {
+    return false;
+  }
+
+  if (!DebugScript::incrementGeneratorObserverCount(cx, script)) {
+    return false;
+  }
+
+  InitReservedSlot(this, GENERATOR_INFO_SLOT, info.release(),
+                   MemoryUse::DebuggerFrameGeneratorInfo);
+  return true;
+}
+
+void DebuggerFrame::terminate(JSFreeOp* fop, AbstractFramePtr frame) {
+  if (frameIterData()) {
+    // If no frame pointer was provided to decrement the stepper counter,
+    // then we must be terminating a generator, otherwise the stepper count
+    // would have no way to synchronize properly.
+    MOZ_ASSERT_IF(!frame, hasGeneratorInfo());
+
+    freeFrameIterData(fop);
+    if (frame && !hasGeneratorInfo() && onStepHandler()) {
+      // If we are terminating a non-generator frame that had a step handler,
+      // we need to decrement the counter to keep things in sync.
+      decrementStepperCounter(fop, frame);
+    }
+  }
+
+  if (!hasGeneratorInfo()) {
+    return;
+  }
+
+  GeneratorInfo* info = generatorInfo();
+
+  // 3) The generator's script's observer count must be dropped.
+  //
+  // For ordinary calls, Debugger.Frame objects drop the script's stepper count
+  // when the frame is popped, but for generators, they leave the stepper count
+  // incremented across suspensions. This means that, whereas ordinary calls
+  // never need to drop the stepper count from the D.F finalizer, generator
+  // calls may.
+  if (!info->isGeneratorScriptAboutToBeFinalized()) {
+    JSScript* generatorScript = info->generatorScript();
+    DebugScript::decrementGeneratorObserverCount(fop, generatorScript);
+    if (onStepHandler()) {
+      // If we are terminating a generator frame that had a step handler,
+      // we need to decrement the counter to keep things in sync.
+      decrementStepperCounter(fop, generatorScript);
+    }
+  }
+
+  // 1) The DebuggerFrame must no longer point to the AbstractGeneratorObject.
+  setReservedSlot(GENERATOR_INFO_SLOT, UndefinedValue());
+  fop->delete_(this, info, MemoryUse::DebuggerFrameGeneratorInfo);
+}
+
+void DebuggerFrame::suspend(JSFreeOp* fop) {
+  // There must be generator info because otherwise this would be the same
+  // overall behavior as terminate() except that here we do not properly
+  // adjust stepper counts.
+  MOZ_ASSERT(hasGeneratorInfo());
+
+  freeFrameIterData(fop);
+}
+
+/* static */
+bool DebuggerFrame::getCallee(JSContext* cx, HandleDebuggerFrame frame,
+                              MutableHandleDebuggerObject result) {
+  RootedObject callee(cx);
+  if (frame->isOnStack()) {
+    AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+    if (referent.isFunctionFrame()) {
+      callee = referent.callee();
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    callee = &frame->generatorInfo()->unwrappedGenerator().callee();
+  }
+
+  return frame->owner()->wrapNullableDebuggeeObject(cx, callee, result);
+}
+
+/* static */
+bool DebuggerFrame::getIsConstructing(JSContext* cx, HandleDebuggerFrame frame,
+                                      bool& result) {
+  if (frame->isOnStack()) {
+    FrameIter iter = frame->getFrameIter(cx);
+
+    result = iter.isFunctionFrame() && iter.isConstructing();
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    // Generators and async functions can't be constructed.
+    result = false;
+  }
+  return true;
+}
+
+static void UpdateFrameIterPc(FrameIter& iter) {
+  if (iter.abstractFramePtr().isWasmDebugFrame()) {
+    // Wasm debug frames don't need their pc updated -- it's null.
+    return;
+  }
+
+  if (iter.abstractFramePtr().isRematerializedFrame()) {
+#ifdef DEBUG
+    // Rematerialized frames don't need their pc updated. The reason we
+    // need to update pc is because we might get the same Debugger.Frame
+    // object for multiple re-entries into debugger code from debuggee
+    // code. This reentrancy is not possible with rematerialized frames,
+    // because when returning to debuggee code, we would have bailed out
+    // to baseline.
+    //
+    // We walk the stack to assert that it doesn't need updating.
+    jit::RematerializedFrame* frame =
+        iter.abstractFramePtr().asRematerializedFrame();
+    jit::JitFrameLayout* jsFrame = (jit::JitFrameLayout*)frame->top();
+    jit::JitActivation* activation = iter.activation()->asJit();
+
+    JSContext* cx = TlsContext.get();
+    MOZ_ASSERT(cx == activation->cx());
+
+    ActivationIterator activationIter(cx);
+    while (activationIter.activation() != activation) {
+      ++activationIter;
+    }
+
+    OnlyJSJitFrameIter jitIter(activationIter);
+    while (!jitIter.frame().isIonJS() || jitIter.frame().jsFrame() != jsFrame) {
+      ++jitIter;
+    }
+
+    jit::InlineFrameIterator ionInlineIter(cx, &jitIter.frame());
+    while (ionInlineIter.frameNo() != frame->frameNo()) {
+      ++ionInlineIter;
+    }
+
+    MOZ_ASSERT(ionInlineIter.pc() == iter.pc());
+#endif
+    return;
+  }
+
+  iter.updatePcQuadratic();
+}
+
+/* static */
+bool DebuggerFrame::getEnvironment(JSContext* cx, HandleDebuggerFrame frame,
+                                   MutableHandleDebuggerEnvironment result) {
+  Debugger* dbg = frame->owner();
+  Rooted<Env*> env(cx);
+
+  if (frame->isOnStack()) {
+    FrameIter iter = frame->getFrameIter(cx);
+
+    {
+      AutoRealm ar(cx, iter.abstractFramePtr().environmentChain());
+      UpdateFrameIterPc(iter);
+      env = GetDebugEnvironmentForFrame(cx, iter.abstractFramePtr(), iter.pc());
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    AbstractGeneratorObject& genObj =
+        frame->generatorInfo()->unwrappedGenerator();
+    JSScript* script = frame->generatorInfo()->generatorScript();
+
+    {
+      AutoRealm ar(cx, &genObj.environmentChain());
+      env = GetDebugEnvironmentForSuspendedGenerator(cx, script, genObj);
+    }
+  }
+
+  if (!env) {
+    return false;
+  }
+
+  return dbg->wrapEnvironment(cx, env, result);
+}
+
+/* static */
+bool DebuggerFrame::getOffset(JSContext* cx, HandleDebuggerFrame frame,
+                              size_t& result) {
+  if (frame->isOnStack()) {
+    FrameIter iter = frame->getFrameIter(cx);
+
+    AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+    if (referent.isWasmDebugFrame()) {
+      iter.wasmUpdateBytecodeOffset();
+      result = iter.wasmBytecodeOffset();
+    } else {
+      JSScript* script = iter.script();
+      UpdateFrameIterPc(iter);
+      jsbytecode* pc = iter.pc();
+      result = script->pcToOffset(pc);
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    AbstractGeneratorObject& genObj =
+        frame->generatorInfo()->unwrappedGenerator();
+    JSScript* script = frame->generatorInfo()->generatorScript();
+    result = script->resumeOffsets()[genObj.resumeIndex()];
+  }
+  return true;
+}
+
+/* static */
+bool DebuggerFrame::getOlder(JSContext* cx, HandleDebuggerFrame frame,
+                             MutableHandleDebuggerFrame result) {
+  if (frame->isOnStack()) {
+    Debugger* dbg = frame->owner();
+    FrameIter iter = frame->getFrameIter(cx);
+
+    while (true) {
+      Activation& activation = *iter.activation();
+      ++iter;
+
+      // If the parent frame crosses an explicit async stack boundary, we
+      // treat that as an indication to stop traversing sync frames, so that
+      // the on-stack Debugger.Frame instances align with what you would
+      // see in a stringified stack trace.
+      if (iter.activation() != &activation && activation.asyncStack() &&
+          activation.asyncCallIsExplicit()) {
+        break;
+      }
+
+      // If there is no parent frame, we're done.
+      if (iter.done()) {
+        break;
+      }
+
+      if (dbg->observesFrame(iter)) {
+        if (iter.isIon() && !iter.ensureHasRematerializedFrame(cx)) {
+          return false;
+        }
+        return dbg->getFrame(cx, iter, result);
+      }
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    // If the frame is suspended, there is no older frame.
+  }
+
+  result.set(nullptr);
+  return true;
+}
+
+/* static */
+bool DebuggerFrame::getAsyncPromise(JSContext* cx, HandleDebuggerFrame frame,
+                                    MutableHandleDebuggerObject result) {
+  MOZ_ASSERT(frame->isOnStack() || frame->isSuspended());
+
+  if (!frame->hasGeneratorInfo()) {
+    // An on-stack frame may not have an associated generator yet when the
+    // frame is initially entered.
+    result.set(nullptr);
+    return true;
+  }
+
+  RootedObject resultObject(cx);
+  AbstractGeneratorObject& generator = frame->unwrappedGenerator();
+  if (generator.is<AsyncFunctionGeneratorObject>()) {
+    resultObject = generator.as<AsyncFunctionGeneratorObject>().promise();
+  } else if (generator.is<AsyncGeneratorObject>()) {
+    Rooted<AsyncGeneratorObject*> asyncGen(
+        cx, &generator.as<AsyncGeneratorObject>());
+    // In initial function execution, there is no promise.
+    if (!asyncGen->isQueueEmpty()) {
+      resultObject = AsyncGeneratorObject::peekRequest(asyncGen)->promise();
+    }
+  } else {
+    MOZ_CRASH("Unknown async generator type");
+  }
+
+  return frame->owner()->wrapNullableDebuggeeObject(cx, resultObject, result);
+}
+
+/* static */
+bool DebuggerFrame::getThis(JSContext* cx, HandleDebuggerFrame frame,
+                            MutableHandleValue result) {
+  Debugger* dbg = frame->owner();
+
+  if (frame->isOnStack()) {
+    if (!requireScriptReferent(cx, frame)) {
+      return false;
+    }
+    FrameIter iter = frame->getFrameIter(cx);
+
+    {
+      AbstractFramePtr frame = iter.abstractFramePtr();
+      AutoRealm ar(cx, frame.environmentChain());
+
+      UpdateFrameIterPc(iter);
+
+      if (!GetThisValueForDebuggerFrameMaybeOptimizedOut(cx, frame, iter.pc(),
+                                                         result)) {
+        return false;
+      }
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    AbstractGeneratorObject& genObj =
+        frame->generatorInfo()->unwrappedGenerator();
+    AutoRealm ar(cx, &genObj);
+    JSScript* script = frame->generatorInfo()->generatorScript();
+
+    if (!GetThisValueForDebuggerSuspendedGeneratorMaybeOptimizedOut(
+            cx, genObj, script, result)) {
+      return false;
+    }
+  }
+
+  return dbg->wrapDebuggeeValue(cx, result);
+}
+
+/* static */
+DebuggerFrameType DebuggerFrame::getType(HandleDebuggerFrame frame) {
+  if (frame->isOnStack()) {
+    AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+
+    // Indirect eval frames are both isGlobalFrame() and isEvalFrame(), so the
+    // order of checks here is significant.
+    if (referent.isEvalFrame()) {
+      return DebuggerFrameType::Eval;
+    }
+
+    if (referent.isGlobalFrame()) {
+      return DebuggerFrameType::Global;
+    }
+
+    if (referent.isFunctionFrame()) {
+      return DebuggerFrameType::Call;
+    }
+
+    if (referent.isModuleFrame()) {
+      return DebuggerFrameType::Module;
+    }
+
+    if (referent.isWasmDebugFrame()) {
+      return DebuggerFrameType::WasmCall;
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+
+    return DebuggerFrameType::Call;
+  }
+
+  MOZ_CRASH("Unknown frame type");
+}
+
+/* static */
+DebuggerFrameImplementation DebuggerFrame::getImplementation(
+    HandleDebuggerFrame frame) {
+  AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+
+  if (referent.isBaselineFrame()) {
+    return DebuggerFrameImplementation::Baseline;
+  }
+
+  if (referent.isRematerializedFrame()) {
+    return DebuggerFrameImplementation::Ion;
+  }
+
+  if (referent.isWasmDebugFrame()) {
+    return DebuggerFrameImplementation::Wasm;
+  }
+
+  return DebuggerFrameImplementation::Interpreter;
+}
+
+/*
+ * If succesful, transfers the ownership of the given `handler` to this
+ * Debugger.Frame. Note that on failure, the ownership of `handler` is not
+ * transferred, and the caller is responsible for cleaning it up.
+ */
+/* static */
+bool DebuggerFrame::setOnStepHandler(JSContext* cx, HandleDebuggerFrame frame,
+                                     OnStepHandler* handler) {
+  OnStepHandler* prior = frame->onStepHandler();
+  if (handler == prior) {
+    return true;
+  }
+
+  JSFreeOp* fop = cx->defaultFreeOp();
+  if (frame->isOnStack()) {
+    AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+
+    // Adjust execution observability and step counts on whatever code (JS or
+    // Wasm) this frame is running.
+    if (handler && !prior) {
+      if (!frame->incrementStepperCounter(cx, referent)) {
+        return false;
+      }
+    } else if (!handler && prior) {
+      frame->decrementStepperCounter(cx->runtime()->defaultFreeOp(), referent);
+    }
+  } else if (frame->isSuspended()) {
+    RootedScript script(cx, frame->generatorInfo()->generatorScript());
+
+    if (handler && !prior) {
+      if (!frame->incrementStepperCounter(cx, script)) {
+        return false;
+      }
+    } else if (!handler && prior) {
+      frame->decrementStepperCounter(cx->runtime()->defaultFreeOp(), script);
+    }
+  } else {
+    // If the frame is entirely dead, we still allow setting the onStep
+    // handler, but it has no effect.
+  }
+
+  // Now that the stepper counts and observability are set correctly, we can
+  // actually switch the handler.
+  if (prior) {
+    prior->drop(fop, frame);
+  }
+
+  if (handler) {
+    frame->setReservedSlot(ONSTEP_HANDLER_SLOT, PrivateValue(handler));
+    handler->hold(frame);
+  } else {
+    frame->setReservedSlot(ONSTEP_HANDLER_SLOT, UndefinedValue());
+  }
+
+  return true;
+}
+
+bool DebuggerFrame::incrementStepperCounter(JSContext* cx,
+                                            AbstractFramePtr referent) {
+  if (!referent.isWasmDebugFrame()) {
+    return incrementStepperCounter(cx, referent.script());
+  }
+
+  wasm::Instance* instance = referent.asWasmDebugFrame()->instance();
+  wasm::DebugFrame* wasmFrame = referent.asWasmDebugFrame();
+  // Single stepping toggled off->on.
+  if (!instance->debug().incrementStepperCount(cx, wasmFrame->funcIndex())) {
+    return false;
+  }
+
+  return true;
+}
+
+bool DebuggerFrame::incrementStepperCounter(JSContext* cx, JSScript* script) {
+  // Single stepping toggled off->on.
+  AutoRealm ar(cx, script);
+  // Ensure observability *before* incrementing the step mode count.
+  // Calling this function after calling incrementStepperCount
+  // will make it a no-op.
+  if (!Debugger::ensureExecutionObservabilityOfScript(cx, script)) {
+    return false;
+  }
+  if (!DebugScript::incrementStepperCount(cx, script)) {
+    return false;
+  }
+
+  return true;
+}
+
+void DebuggerFrame::decrementStepperCounter(JSFreeOp* fop,
+                                            AbstractFramePtr referent) {
+  if (!referent.isWasmDebugFrame()) {
+    decrementStepperCounter(fop, referent.script());
+    return;
+  }
+
+  wasm::Instance* instance = referent.asWasmDebugFrame()->instance();
+  wasm::DebugFrame* wasmFrame = referent.asWasmDebugFrame();
+  // Single stepping toggled on->off.
+  instance->debug().decrementStepperCount(fop, wasmFrame->funcIndex());
+}
+
+void DebuggerFrame::decrementStepperCounter(JSFreeOp* fop, JSScript* script) {
+  // Single stepping toggled on->off.
+  DebugScript::decrementStepperCount(fop, script);
+}
+
+/* static */
+bool DebuggerFrame::getArguments(JSContext* cx, HandleDebuggerFrame frame,
+                                 MutableHandleDebuggerArguments result) {
+  Value argumentsv = frame->getReservedSlot(ARGUMENTS_SLOT);
+  if (!argumentsv.isUndefined()) {
+    result.set(argumentsv.isObject()
+                   ? &argumentsv.toObject().as<DebuggerArguments>()
+                   : nullptr);
+    return true;
+  }
+
+  AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+
+  RootedDebuggerArguments arguments(cx);
+  if (referent.hasArgs()) {
+    Rooted<GlobalObject*> global(cx, &frame->global());
+    RootedObject proto(cx, GlobalObject::getOrCreateArrayPrototype(cx, global));
+    if (!proto) {
+      return false;
+    }
+    arguments = DebuggerArguments::create(cx, proto, frame);
+    if (!arguments) {
+      return false;
+    }
+  } else {
+    arguments = nullptr;
+  }
+
+  result.set(arguments);
+  frame->setReservedSlot(ARGUMENTS_SLOT, ObjectOrNullValue(result));
+  return true;
+}
+
+/*
+ * Evaluate |chars[0..length-1]| in the environment |env|, treating that
+ * source as appearing starting at |lineno| in |filename|. Store the return
+ * value in |*rval|. Use |thisv| as the 'this' value.
+ *
+ * If |frame| is non-nullptr, evaluate as for a direct eval in that frame; |env|
+ * must be either |frame|'s DebugScopeObject, or some extension of that
+ * environment; either way, |frame|'s scope is where newly declared variables
+ * go. In this case, |frame| must have a computed 'this' value, equal to
+ * |thisv|.
+ */
+static bool EvaluateInEnv(JSContext* cx, Handle<Env*> env,
+                          AbstractFramePtr frame,
+                          mozilla::Range<const char16_t> chars,
+                          const char* filename, unsigned lineno,
+                          MutableHandleValue rval) {
+  cx->check(env, frame);
+
+  CompileOptions options(cx);
+  options.setIsRunOnce(true)
+      .setNoScriptRval(false)
+      .setFileAndLine(filename, lineno)
+      .setIntroductionType("debugger eval")
+      /* Do not perform the Javascript filename validation security check for
+       * javascript executions sent through the debugger. Besides making up
+       * a filename for these codepaths, we must allow arbitrary JS execution
+       * for the Browser toolbox to function. */
+      .setSkipFilenameValidation(true);
+
+  if (frame && frame.hasScript() && frame.script()->strict()) {
+    options.setForceStrictMode();
+  }
+
+  SourceText<char16_t> srcBuf;
+  if (!srcBuf.init(cx, chars.begin().get(), chars.length(),
+                   SourceOwnership::Borrowed)) {
+    return false;
+  }
+
+  RootedScript callerScript(
+      cx, frame && frame.hasScript() ? frame.script() : nullptr);
+  RootedScript script(cx);
+
+  ScopeKind scopeKind;
+  if (IsGlobalLexicalEnvironment(env)) {
+    scopeKind = ScopeKind::Global;
+  } else {
+    scopeKind = ScopeKind::NonSyntactic;
+    options.setNonSyntacticScope(true);
+  }
+
+  if (frame) {
+    MOZ_ASSERT(scopeKind == ScopeKind::NonSyntactic);
+    RootedScope scope(cx,
+                      GlobalScope::createEmpty(cx, ScopeKind::NonSyntactic));
+    if (!scope) {
+      return false;
+    }
+
+    script = frontend::CompileEvalScript(cx, options, srcBuf, scope, env);
+    if (!script) {
+      return false;
+    }
+  } else {
+    // Do not consider executeInGlobal{WithBindings} as an eval, but instead
+    // as executing a series of statements at the global level. This is to
+    // circumvent the fresh lexical scope that all eval have, so that the
+    // users of executeInGlobal, like the web console, may add new bindings to
+    // the global scope.
+
+    MOZ_ASSERT(scopeKind == ScopeKind::Global ||
+               scopeKind == ScopeKind::NonSyntactic);
+
+    script = frontend::CompileGlobalScript(cx, options, srcBuf, scopeKind);
+    if (!script) {
+      return false;
+    }
+  }
+
+  // Note: pass NullHandleValue for newTarget because the parser doesn't accept
+  // new.target in debugger eval frames (bug 1169076). Once that changes we need
+  // to compute newTarget here based on |frame|.
+  return ExecuteKernel(cx, script, env, NullHandleValue, frame, rval);
+}
+
+Result<Completion> js::DebuggerGenericEval(
+    JSContext* cx, const mozilla::Range<const char16_t> chars,
+    HandleObject bindings, const EvalOptions& options, Debugger* dbg,
+    HandleObject envArg, FrameIter* iter) {
+  // Either we're specifying the frame, or a global.
+  MOZ_ASSERT_IF(iter, !envArg);
+  MOZ_ASSERT_IF(!iter, envArg && IsGlobalLexicalEnvironment(envArg));
+
+  // Gather keys and values of bindings, if any. This must be done in the
+  // debugger compartment, since that is where any exceptions must be thrown.
+  RootedIdVector keys(cx);
+  RootedValueVector values(cx);
+  if (bindings) {
+    if (!GetPropertyKeys(cx, bindings, JSITER_OWNONLY, &keys) ||
+        !values.growBy(keys.length())) {
+      return cx->alreadyReportedError();
+    }
+    for (size_t i = 0; i < keys.length(); i++) {
+      MutableHandleValue valp = values[i];
+      if (!GetProperty(cx, bindings, bindings, keys[i], valp) ||
+          !dbg->unwrapDebuggeeValue(cx, valp)) {
+        return cx->alreadyReportedError();
+      }
+    }
+  }
+
+  Maybe<AutoRealm> ar;
+  if (iter) {
+    ar.emplace(cx, iter->environmentChain(cx));
+  } else {
+    ar.emplace(cx, envArg);
+  }
+
+  Rooted<Env*> env(cx);
+  if (iter) {
+    env = GetDebugEnvironmentForFrame(cx, iter->abstractFramePtr(), iter->pc());
+    if (!env) {
+      return cx->alreadyReportedError();
+    }
+  } else {
+    env = envArg;
+  }
+
+  // If evalWithBindings, create the inner environment.
+  if (bindings) {
+    RootedPlainObject nenv(cx,
+                           NewObjectWithGivenProto<PlainObject>(cx, nullptr));
+    if (!nenv) {
+      return cx->alreadyReportedError();
+    }
+    RootedId id(cx);
+    for (size_t i = 0; i < keys.length(); i++) {
+      id = keys[i];
+      cx->markId(id);
+      MutableHandleValue val = values[i];
+      if (!cx->compartment()->wrap(cx, val) ||
+          !NativeDefineDataProperty(cx, nenv, id, val, 0)) {
+        return cx->alreadyReportedError();
+      }
+    }
+
+    RootedObjectVector envChain(cx);
+    if (!envChain.append(nenv)) {
+      return cx->alreadyReportedError();
+    }
+
+    RootedObject newEnv(cx);
+    if (!CreateObjectsForEnvironmentChain(cx, envChain, env, &newEnv)) {
+      return cx->alreadyReportedError();
+    }
+
+    env = newEnv;
+  }
+
+  // Note whether we are in an evaluation that might invoke the OnNativeCall
+  // hook, so that the JITs will be disabled.
+  AutoNoteDebuggerEvaluationWithOnNativeCallHook noteEvaluation(
+      cx, dbg->observesNativeCalls() ? dbg : nullptr);
+
+  // Run the code and produce the completion value.
+  LeaveDebuggeeNoExecute nnx(cx);
+  RootedValue rval(cx);
+  AbstractFramePtr frame = iter ? iter->abstractFramePtr() : NullFramePtr();
+
+  bool ok = EvaluateInEnv(
+      cx, env, frame, chars,
+      options.filename() ? options.filename() : "debugger eval code",
+      options.lineno(), &rval);
+  Rooted<Completion> completion(cx, Completion::fromJSResult(cx, ok, rval));
+  ar.reset();
+  return completion.get();
+}
+
+/* static */
+Result<Completion> DebuggerFrame::eval(JSContext* cx, HandleDebuggerFrame frame,
+                                       mozilla::Range<const char16_t> chars,
+                                       HandleObject bindings,
+                                       const EvalOptions& options) {
+  MOZ_ASSERT(frame->isOnStack());
+
+  Debugger* dbg = frame->owner();
+  FrameIter iter = frame->getFrameIter(cx);
+
+  UpdateFrameIterPc(iter);
+
+  return DebuggerGenericEval(cx, chars, bindings, options, dbg, nullptr, &iter);
+}
+
+bool DebuggerFrame::isOnStack() const { return !!getPrivate(); }
+
+bool DebuggerFrame::isOnStackMaybeForwarded() const {
+  return !!getPrivateMaybeForwarded();
+}
+
+OnStepHandler* DebuggerFrame::onStepHandler() const {
+  Value value = getReservedSlot(ONSTEP_HANDLER_SLOT);
+  return value.isUndefined() ? nullptr
+                             : static_cast<OnStepHandler*>(value.toPrivate());
+}
+
+OnPopHandler* DebuggerFrame::onPopHandler() const {
+  Value value = getReservedSlot(ONPOP_HANDLER_SLOT);
+  return value.isUndefined() ? nullptr
+                             : static_cast<OnPopHandler*>(value.toPrivate());
+}
+
+void DebuggerFrame::setOnPopHandler(JSContext* cx, OnPopHandler* handler) {
+  OnPopHandler* prior = onPopHandler();
+  if (handler == prior) {
+    return;
+  }
+
+  JSFreeOp* fop = cx->defaultFreeOp();
+
+  if (prior) {
+    prior->drop(fop, this);
+  }
+
+  if (handler) {
+    setReservedSlot(ONPOP_HANDLER_SLOT, PrivateValue(handler));
+    handler->hold(this);
+  } else {
+    setReservedSlot(ONPOP_HANDLER_SLOT, UndefinedValue());
+  }
+}
+
+FrameIter::Data* DebuggerFrame::frameIterData() const {
+  return static_cast<FrameIter::Data*>(getPrivate());
+}
+
+/* static */
+AbstractFramePtr DebuggerFrame::getReferent(HandleDebuggerFrame frame) {
+  FrameIter iter(*frame->frameIterData());
+  return iter.abstractFramePtr();
+}
+
+FrameIter DebuggerFrame::getFrameIter(JSContext* cx) {
+  FrameIter::Data* data = frameIterData();
+  MOZ_ASSERT(data);
+  MOZ_ASSERT(data->cx_ == cx);
+
+  return FrameIter(*data);
+}
+
+/* static */
+bool DebuggerFrame::requireScriptReferent(JSContext* cx,
+                                          HandleDebuggerFrame frame) {
+  AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+  if (!referent.hasScript()) {
+    RootedValue frameobj(cx, ObjectValue(*frame));
+    ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK, frameobj,
+                     nullptr, "a script frame");
+    return false;
+  }
+  return true;
+}
+
+void DebuggerFrame::setFrameIterData(FrameIter::Data* data) {
+  MOZ_ASSERT(data);
+  MOZ_ASSERT(!frameIterData());
+  InitObjectPrivate(this, data, MemoryUse::DebuggerFrameIterData);
+}
+
+void DebuggerFrame::freeFrameIterData(JSFreeOp* fop) {
+  if (FrameIter::Data* data = frameIterData()) {
+    fop->delete_(this, data, MemoryUse::DebuggerFrameIterData);
+    setPrivate(nullptr);
+  }
+}
+
+bool DebuggerFrame::replaceFrameIterData(JSContext* cx, const FrameIter& iter) {
+  FrameIter::Data* data = iter.copyData();
+  if (!data) {
+    return false;
+  }
+  freeFrameIterData(cx->runtime()->defaultFreeOp());
+  setFrameIterData(data);
+  return true;
+}
+
+/* static */
+void DebuggerFrame::finalize(JSFreeOp* fop, JSObject* obj) {
+  MOZ_ASSERT(fop->onMainThread());
+
+  DebuggerFrame& frameobj = obj->as<DebuggerFrame>();
+
+  // Connections between dying Debugger.Frames and their
+  // AbstractGeneratorObjects, as well as the frame's stack data should have
+  // been by a call to terminate() from sweepAll or some other place.
+  MOZ_ASSERT(!frameobj.hasGeneratorInfo());
+  MOZ_ASSERT(!frameobj.frameIterData());
+  OnStepHandler* onStepHandler = frameobj.onStepHandler();
+  if (onStepHandler) {
+    onStepHandler->drop(fop, &frameobj);
+  }
+  OnPopHandler* onPopHandler = frameobj.onPopHandler();
+  if (onPopHandler) {
+    onPopHandler->drop(fop, &frameobj);
+  }
+}
+
+void DebuggerFrame::trace(JSTracer* trc) {
+  OnStepHandler* onStepHandler = this->onStepHandler();
+  if (onStepHandler) {
+    onStepHandler->trace(trc);
+  }
+  OnPopHandler* onPopHandler = this->onPopHandler();
+  if (onPopHandler) {
+    onPopHandler->trace(trc);
+  }
+
+  if (hasGeneratorInfo()) {
+    generatorInfo()->trace(trc, *this);
+  }
+}
+
+/* static */
+DebuggerFrame* DebuggerFrame::check(JSContext* cx, HandleValue thisv) {
+  JSObject* thisobj = RequireObject(cx, thisv);
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerFrame>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Frame",
+                              "method", thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  RootedDebuggerFrame frame(cx, &thisobj->as<DebuggerFrame>());
+
+  // Forbid Debugger.Frame.prototype, which is of class DebuggerFrame::class_
+  // but isn't really a working Debugger.Frame object.
+  if (!frame->isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Frame",
+                              "method", "prototype object");
+    return nullptr;
+  }
+
+  return frame;
+}
+
+struct MOZ_STACK_CLASS DebuggerFrame::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  HandleDebuggerFrame frame;
+
+  CallData(JSContext* cx, const CallArgs& args, HandleDebuggerFrame frame)
+      : cx(cx), args(args), frame(frame) {}
+
+  bool argumentsGetter();
+  bool calleeGetter();
+  bool constructingGetter();
+  bool environmentGetter();
+  bool generatorGetter();
+  bool asyncPromiseGetter();
+  bool olderSavedFrameGetter();
+  bool liveGetter();
+  bool onStackGetter();
+  bool terminatedGetter();
+  bool offsetGetter();
+  bool olderGetter();
+  bool getScript();
+  bool thisGetter();
+  bool typeGetter();
+  bool implementationGetter();
+  bool onStepGetter();
+  bool onStepSetter();
+  bool onPopGetter();
+  bool onPopSetter();
+  bool evalMethod();
+  bool evalWithBindingsMethod();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+
+  bool ensureOnStack() const;
+  bool ensureOnStackOrSuspended() const;
+};
+
+template <DebuggerFrame::CallData::Method MyMethod>
+/* static */
+bool DebuggerFrame::CallData::ToNative(JSContext* cx, unsigned argc,
+                                       Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedDebuggerFrame frame(cx, DebuggerFrame::check(cx, args.thisv()));
+  if (!frame) {
+    return false;
+  }
+
+  CallData data(cx, args, frame);
+  return (data.*MyMethod)();
+}
+
+static bool EnsureOnStack(JSContext* cx, HandleDebuggerFrame frame) {
+  MOZ_ASSERT(frame);
+  if (!frame->isOnStack()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_NOT_ON_STACK, "Debugger.Frame");
+    return false;
+  }
+
+  return true;
+}
+static bool EnsureOnStackOrSuspended(JSContext* cx, HandleDebuggerFrame frame) {
+  MOZ_ASSERT(frame);
+  if (!frame->isOnStack() && !frame->isSuspended()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_NOT_ON_STACK_OR_SUSPENDED,
+                              "Debugger.Frame");
+    return false;
+  }
+
+  return true;
+}
+
+bool DebuggerFrame::CallData::ensureOnStack() const {
+  return EnsureOnStack(cx, frame);
+}
+bool DebuggerFrame::CallData::ensureOnStackOrSuspended() const {
+  return EnsureOnStackOrSuspended(cx, frame);
+}
+
+bool DebuggerFrame::CallData::typeGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  DebuggerFrameType type = DebuggerFrame::getType(frame);
+
+  JSString* str;
+  switch (type) {
+    case DebuggerFrameType::Eval:
+      str = cx->names().eval;
+      break;
+    case DebuggerFrameType::Global:
+      str = cx->names().global;
+      break;
+    case DebuggerFrameType::Call:
+      str = cx->names().call;
+      break;
+    case DebuggerFrameType::Module:
+      str = cx->names().module;
+      break;
+    case DebuggerFrameType::WasmCall:
+      str = cx->names().wasmcall;
+      break;
+    default:
+      MOZ_CRASH("bad DebuggerFrameType value");
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+bool DebuggerFrame::CallData::implementationGetter() {
+  if (!ensureOnStack()) {
+    return false;
+  }
+
+  DebuggerFrameImplementation implementation =
+      DebuggerFrame::getImplementation(frame);
+
+  const char* s;
+  switch (implementation) {
+    case DebuggerFrameImplementation::Baseline:
+      s = "baseline";
+      break;
+    case DebuggerFrameImplementation::Ion:
+      s = "ion";
+      break;
+    case DebuggerFrameImplementation::Interpreter:
+      s = "interpreter";
+      break;
+    case DebuggerFrameImplementation::Wasm:
+      s = "wasm";
+      break;
+    default:
+      MOZ_CRASH("bad DebuggerFrameImplementation value");
+  }
+
+  JSAtom* str = Atomize(cx, s, strlen(s));
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  return true;
+}
+
+bool DebuggerFrame::CallData::environmentGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedDebuggerEnvironment result(cx);
+  if (!DebuggerFrame::getEnvironment(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerFrame::CallData::calleeGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedDebuggerObject result(cx);
+  if (!DebuggerFrame::getCallee(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerFrame::CallData::generatorGetter() {
+  JS_ReportErrorASCII(cx,
+                      "Debugger.Frame.prototype.generator has been removed. "
+                      "Use frame.script.isGeneratorFunction instead.");
+  return false;
+}
+
+bool DebuggerFrame::CallData::constructingGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  bool result;
+  if (!DebuggerFrame::getIsConstructing(cx, frame, result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool DebuggerFrame::CallData::asyncPromiseGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedScript script(cx);
+  if (frame->isOnStack()) {
+    FrameIter iter = frame->getFrameIter(cx);
+    AbstractFramePtr framePtr = iter.abstractFramePtr();
+
+    if (!framePtr.isWasmDebugFrame()) {
+      script = framePtr.script();
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+    script = frame->generatorInfo()->generatorScript();
+  }
+  // The async promise value is only provided for async functions and
+  // async generator functions.
+  if (!script || !script->isAsync()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedDebuggerObject result(cx);
+  if (!DebuggerFrame::getAsyncPromise(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerFrame::CallData::olderSavedFrameGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedSavedFrame result(cx);
+  if (!DebuggerFrame::getOlderSavedFrame(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+/* static */
+bool DebuggerFrame::getOlderSavedFrame(JSContext* cx, HandleDebuggerFrame frame,
+                                       MutableHandleSavedFrame result) {
+  if (frame->isOnStack()) {
+    Debugger* dbg = frame->owner();
+    FrameIter iter = frame->getFrameIter(cx);
+
+    while (true) {
+      Activation& activation = *iter.activation();
+      ++iter;
+
+      // If the parent frame crosses an explicit async stack boundary, or we
+      // have hit the end of the synchronous frames, we want to switch over
+      // to using SavedFrames.
+      if (iter.activation() != &activation && activation.asyncStack() &&
+          (activation.asyncCallIsExplicit() || iter.done())) {
+        const char* cause = activation.asyncCause();
+        RootedAtom causeAtom(cx, AtomizeUTF8Chars(cx, cause, strlen(cause)));
+        if (!causeAtom) {
+          return false;
+        }
+        RootedSavedFrame stackObj(cx, activation.asyncStack());
+
+        return cx->realm()->savedStacks().copyAsyncStack(
+            cx, stackObj, causeAtom, result, mozilla::Nothing());
+      }
+
+      // If there are no more parent frames, we're done.
+      if (iter.done()) {
+        break;
+      }
+
+      // If we hit another frame that we observe, then there is no saved
+      // frame that we'd want to return.
+      if (dbg->observesFrame(iter)) {
+        break;
+      }
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+  }
+
+  result.set(nullptr);
+  return true;
+}
+
+bool DebuggerFrame::CallData::thisGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  return DebuggerFrame::getThis(cx, frame, args.rval());
+}
+
+bool DebuggerFrame::CallData::olderGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedDebuggerFrame result(cx);
+  if (!DebuggerFrame::getOlder(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+// The getter used for each element of frame.arguments.
+// See DebuggerFrame::getArguments.
+static bool DebuggerArguments_getArg(JSContext* cx, unsigned argc, Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+  int32_t i = args.callee().as<JSFunction>().getExtendedSlot(0).toInt32();
+
+  // Check that the this value is an Arguments object.
+  RootedObject argsobj(cx, RequireObject(cx, args.thisv()));
+  if (!argsobj) {
+    return false;
+  }
+  if (argsobj->getClass() != &DebuggerArguments::class_) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Arguments",
+                              "getArgument", argsobj->getClass()->name);
+    return false;
+  }
+
+  RootedValue framev(cx, argsobj->as<NativeObject>().getReservedSlot(
+                             JSSLOT_DEBUGARGUMENTS_FRAME));
+  RootedDebuggerFrame thisobj(cx, DebuggerFrame::check(cx, framev));
+  if (!thisobj || !EnsureOnStack(cx, thisobj)) {
+    return false;
+  }
+
+  FrameIter iter = thisobj->getFrameIter(cx);
+  AbstractFramePtr frame = iter.abstractFramePtr();
+
+  // TODO handle wasm frame arguments -- they are not yet reflectable.
+  MOZ_ASSERT(!frame.isWasmDebugFrame(), "a wasm frame args");
+
+  // Since getters can be extracted and applied to other objects,
+  // there is no guarantee this object has an ith argument.
+  MOZ_ASSERT(i >= 0);
+  RootedValue arg(cx);
+  RootedScript script(cx);
+  if (unsigned(i) < frame.numActualArgs()) {
+    script = frame.script();
+    {
+      AutoRealm ar(cx, script);
+      if (!script->ensureHasAnalyzedArgsUsage(cx)) {
+        return false;
+      }
+    }
+    if (unsigned(i) < frame.numFormalArgs()) {
+      for (PositionalFormalParameterIter fi(script); fi; fi++) {
+        if (fi.argumentSlot() == unsigned(i)) {
+          // We might've been called before the CallObject was
+          // created.
+          if (fi.closedOver() && frame.hasInitialEnvironment()) {
+            arg = frame.callObj().aliasedBinding(fi);
+          } else {
+            arg = frame.unaliasedActual(i, DONT_CHECK_ALIASING);
+          }
+          break;
+        }
+      }
+    } else if (script->argsObjAliasesFormals() && frame.hasArgsObj()) {
+      arg = frame.argsObj().arg(i);
+    } else {
+      arg = frame.unaliasedActual(i, DONT_CHECK_ALIASING);
+    }
+  } else {
+    arg.setUndefined();
+  }
+
+  if (!thisobj->owner()->wrapDebuggeeValue(cx, &arg)) {
+    return false;
+  }
+  args.rval().set(arg);
+  return true;
+}
+
+/* static */
+DebuggerArguments* DebuggerArguments::create(JSContext* cx, HandleObject proto,
+                                             HandleDebuggerFrame frame) {
+  AbstractFramePtr referent = DebuggerFrame::getReferent(frame);
+
+  Rooted<DebuggerArguments*> obj(
+      cx, NewObjectWithGivenProto<DebuggerArguments>(cx, proto));
+  if (!obj) {
+    return nullptr;
+  }
+
+  JS::SetReservedSlot(obj, FRAME_SLOT, ObjectValue(*frame));
+
+  MOZ_ASSERT(referent.numActualArgs() <= 0x7fffffff);
+  unsigned fargc = referent.numActualArgs();
+  RootedValue fargcVal(cx, Int32Value(fargc));
+  if (!NativeDefineDataProperty(cx, obj, cx->names().length, fargcVal,
+                                JSPROP_PERMANENT | JSPROP_READONLY)) {
+    return nullptr;
+  }
+
+  Rooted<jsid> id(cx);
+  for (unsigned i = 0; i < fargc; i++) {
+    RootedFunction getobj(cx);
+    getobj = NewNativeFunction(cx, DebuggerArguments_getArg, 0, nullptr,
+                               gc::AllocKind::FUNCTION_EXTENDED);
+    if (!getobj) {
+      return nullptr;
+    }
+    id = INT_TO_JSID(i);
+    if (!NativeDefineAccessorProperty(cx, obj, id, getobj, nullptr,
+                                      JSPROP_ENUMERATE | JSPROP_GETTER)) {
+      return nullptr;
+    }
+    getobj->setExtendedSlot(0, Int32Value(i));
+  }
+
+  return obj;
+}
+
+bool DebuggerFrame::CallData::argumentsGetter() {
+  if (!ensureOnStack()) {
+    return false;
+  }
+
+  RootedDebuggerArguments result(cx);
+  if (!DebuggerFrame::getArguments(cx, frame, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerFrame::CallData::getScript() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  RootedDebuggerScript scriptObject(cx);
+
+  Debugger* debug = frame->owner();
+  if (frame->isOnStack()) {
+    FrameIter iter = frame->getFrameIter(cx);
+    AbstractFramePtr framePtr = iter.abstractFramePtr();
+
+    if (framePtr.isWasmDebugFrame()) {
+      RootedWasmInstanceObject instance(cx, framePtr.wasmInstance()->object());
+      scriptObject = debug->wrapWasmScript(cx, instance);
+    } else {
+      RootedScript script(cx, framePtr.script());
+      scriptObject = debug->wrapScript(cx, script);
+    }
+  } else {
+    MOZ_ASSERT(frame->isSuspended());
+    RootedScript script(cx, frame->generatorInfo()->generatorScript());
+    scriptObject = debug->wrapScript(cx, script);
+  }
+  if (!scriptObject) {
+    return false;
+  }
+
+  args.rval().setObject(*scriptObject);
+  return true;
+}
+
+bool DebuggerFrame::CallData::offsetGetter() {
+  if (!ensureOnStackOrSuspended()) {
+    return false;
+  }
+
+  size_t result;
+  if (!DebuggerFrame::getOffset(cx, frame, result)) {
+    return false;
+  }
+
+  args.rval().setNumber(double(result));
+  return true;
+}
+
+bool DebuggerFrame::CallData::liveGetter() {
+  JS_ReportErrorASCII(
+      cx, "Debugger.Frame.prototype.live has been renamed to .onStack");
+  return false;
+}
+
+bool DebuggerFrame::CallData::onStackGetter() {
+  args.rval().setBoolean(frame->isOnStack());
+  return true;
+}
+
+bool DebuggerFrame::CallData::terminatedGetter() {
+  args.rval().setBoolean(!frame->isOnStack() && !frame->isSuspended());
+  return true;
+}
+
+static bool IsValidHook(const Value& v) {
+  return v.isUndefined() || (v.isObject() && v.toObject().isCallable());
+}
+
+bool DebuggerFrame::CallData::onStepGetter() {
+  OnStepHandler* handler = frame->onStepHandler();
+  RootedValue value(
+      cx, handler ? ObjectOrNullValue(handler->object()) : UndefinedValue());
+  MOZ_ASSERT(IsValidHook(value));
+  args.rval().set(value);
+  return true;
+}
+
+bool DebuggerFrame::CallData::onStepSetter() {
+  if (!args.requireAtLeast(cx, "Debugger.Frame.set onStep", 1)) {
+    return false;
+  }
+  if (!IsValidHook(args[0])) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_CALLABLE_OR_UNDEFINED);
+    return false;
+  }
+
+  ScriptedOnStepHandler* handler = nullptr;
+  if (!args[0].isUndefined()) {
+    handler = cx->new_<ScriptedOnStepHandler>(&args[0].toObject());
+    if (!handler) {
+      return false;
+    }
+  }
+
+  if (!DebuggerFrame::setOnStepHandler(cx, frame, handler)) {
+    // Handler has never been successfully associated with the frame so just
+    // delete it rather than calling drop().
+    js_delete(handler);
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerFrame::CallData::onPopGetter() {
+  OnPopHandler* handler = frame->onPopHandler();
+  RootedValue value(
+      cx, handler ? ObjectValue(*handler->object()) : UndefinedValue());
+  MOZ_ASSERT(IsValidHook(value));
+  args.rval().set(value);
+  return true;
+}
+
+bool DebuggerFrame::CallData::onPopSetter() {
+  if (!args.requireAtLeast(cx, "Debugger.Frame.set onPop", 1)) {
+    return false;
+  }
+  if (!IsValidHook(args[0])) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_CALLABLE_OR_UNDEFINED);
+    return false;
+  }
+
+  ScriptedOnPopHandler* handler = nullptr;
+  if (!args[0].isUndefined()) {
+    handler = cx->new_<ScriptedOnPopHandler>(&args[0].toObject());
+    if (!handler) {
+      return false;
+    }
+  }
+
+  frame->setOnPopHandler(cx, handler);
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerFrame::CallData::evalMethod() {
+  if (!ensureOnStack()) {
+    return false;
+  }
+
+  if (!args.requireAtLeast(cx, "Debugger.Frame.prototype.eval", 1)) {
+    return false;
+  }
+
+  AutoStableStringChars stableChars(cx);
+  if (!ValueToStableChars(cx, "Debugger.Frame.prototype.eval", args[0],
+                          stableChars)) {
+    return false;
+  }
+  mozilla::Range<const char16_t> chars = stableChars.twoByteRange();
+
+  EvalOptions options;
+  if (!ParseEvalOptions(cx, args.get(1), options)) {
+    return false;
+  }
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(
+      cx, comp, DebuggerFrame::eval(cx, frame, chars, nullptr, options));
+  return comp.get().buildCompletionValue(cx, frame->owner(), args.rval());
+}
+
+bool DebuggerFrame::CallData::evalWithBindingsMethod() {
+  if (!ensureOnStack()) {
+    return false;
+  }
+
+  if (!args.requireAtLeast(cx, "Debugger.Frame.prototype.evalWithBindings",
+                           2)) {
+    return false;
+  }
+
+  AutoStableStringChars stableChars(cx);
+  if (!ValueToStableChars(cx, "Debugger.Frame.prototype.evalWithBindings",
+                          args[0], stableChars)) {
+    return false;
+  }
+  mozilla::Range<const char16_t> chars = stableChars.twoByteRange();
+
+  RootedObject bindings(cx, RequireObject(cx, args[1]));
+  if (!bindings) {
+    return false;
+  }
+
+  EvalOptions options;
+  if (!ParseEvalOptions(cx, args.get(2), options)) {
+    return false;
+  }
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(
+      cx, comp, DebuggerFrame::eval(cx, frame, chars, bindings, options));
+  return comp.get().buildCompletionValue(cx, frame->owner(), args.rval());
+}
+
+/* static */
+bool DebuggerFrame::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Frame");
+  return false;
+}
+
+const JSPropertySpec DebuggerFrame::properties_[] = {
+    JS_DEBUG_PSG("arguments", argumentsGetter),
+    JS_DEBUG_PSG("callee", calleeGetter),
+    JS_DEBUG_PSG("constructing", constructingGetter),
+    JS_DEBUG_PSG("environment", environmentGetter),
+    JS_DEBUG_PSG("generator", generatorGetter),
+    JS_DEBUG_PSG("live", liveGetter),
+    JS_DEBUG_PSG("onStack", onStackGetter),
+    JS_DEBUG_PSG("terminated", terminatedGetter),
+    JS_DEBUG_PSG("offset", offsetGetter),
+    JS_DEBUG_PSG("older", olderGetter),
+    JS_DEBUG_PSG("olderSavedFrame", olderSavedFrameGetter),
+    JS_DEBUG_PSG("script", getScript),
+    JS_DEBUG_PSG("this", thisGetter),
+    JS_DEBUG_PSG("asyncPromise", asyncPromiseGetter),
+    JS_DEBUG_PSG("type", typeGetter),
+    JS_DEBUG_PSG("implementation", implementationGetter),
+    JS_DEBUG_PSGS("onStep", onStepGetter, onStepSetter),
+    JS_DEBUG_PSGS("onPop", onPopGetter, onPopSetter),
+    JS_PS_END};
+
+const JSFunctionSpec DebuggerFrame::methods_[] = {
+    JS_DEBUG_FN("eval", evalMethod, 1),
+    JS_DEBUG_FN("evalWithBindings", evalWithBindingsMethod, 1), JS_FS_END};
+
+JSObject* js::IdVectorToArray(JSContext* cx, Handle<IdVector> ids) {
+  Rooted<ValueVector> vals(cx, ValueVector(cx));
+  if (!vals.growBy(ids.length())) {
+    return nullptr;
+  }
+
+  for (size_t i = 0, len = ids.length(); i < len; i++) {
+    jsid id = ids[i];
+    if (JSID_IS_INT(id)) {
+      JSString* str = Int32ToString<CanGC>(cx, JSID_TO_INT(id));
+      if (!str) {
+        return nullptr;
+      }
+      vals[i].setString(str);
+    } else if (JSID_IS_ATOM(id)) {
+      vals[i].setString(JSID_TO_STRING(id));
+    } else if (JSID_IS_SYMBOL(id)) {
+      vals[i].setSymbol(JSID_TO_SYMBOL(id));
+    } else {
+      MOZ_ASSERT_UNREACHABLE(
+          "IdVector must contain only string, int, and Symbol jsids");
+    }
+  }
+
+  return NewDenseCopiedArray(cx, vals.length(), vals.begin());
+}
diff --git a/js/src/debugger/Frame.h b/js/src/debugger/Frame.h
new file mode 100644
index 0000000000..886d09b23c
--- /dev/null
+++ b/js/src/debugger/Frame.h
@@ -0,0 +1,300 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Frame_h
+#define debugger_Frame_h
+
+#include "mozilla/Attributes.h"  // for MOZ_MUST_USE
+#include "mozilla/Maybe.h"       // for Maybe
+#include "mozilla/Range.h"       // for Range
+#include "mozilla/Result.h"      // for Result
+
+#include <stddef.h>  // for size_t
+
+#include "jsapi.h"  // for JSContext, CallArgs
+
+#include "NamespaceImports.h"   // for Value, MutableHandleValue, HandleObject
+#include "debugger/DebugAPI.h"  // for ResumeMode
+#include "debugger/Debugger.h"  // for ResumeMode, Handler, Debugger
+#include "gc/Barrier.h"         // for HeapPtr
+#include "gc/Rooting.h"         // for HandleDebuggerFrame, HandleNativeObject
+#include "vm/FrameIter.h"       // for FrameIter
+#include "vm/JSObject.h"        // for JSObject
+#include "vm/NativeObject.h"    // for NativeObject
+#include "vm/Stack.h"           // for AbstractFramePtr
+
+namespace js {
+
+class AbstractGeneratorObject;
+class GlobalObject;
+
+/*
+ * An OnStepHandler represents a handler function that is called when a small
+ * amount of progress is made in a frame.
+ */
+struct OnStepHandler : Handler {
+  /*
+   * If we have made a small amount of progress in a frame, this method is
+   * called with the frame as argument. If succesful, this method should
+   * return true, with `resumeMode` and `vp` set to a resumption value
+   * specifiying how execution should continue.
+   */
+  virtual bool onStep(JSContext* cx, HandleDebuggerFrame frame,
+                      ResumeMode& resumeMode, MutableHandleValue vp) = 0;
+};
+
+class ScriptedOnStepHandler final : public OnStepHandler {
+ public:
+  explicit ScriptedOnStepHandler(JSObject* object);
+  virtual JSObject* object() const override;
+  virtual void hold(JSObject* owner) override;
+  virtual void drop(JSFreeOp* fop, JSObject* owner) override;
+  virtual void trace(JSTracer* tracer) override;
+  virtual size_t allocSize() const override;
+  virtual bool onStep(JSContext* cx, HandleDebuggerFrame frame,
+                      ResumeMode& resumeMode, MutableHandleValue vp) override;
+
+ private:
+  const HeapPtr<JSObject*> object_;
+};
+
+/*
+ * An OnPopHandler represents a handler function that is called just before a
+ * frame is popped.
+ */
+struct OnPopHandler : Handler {
+  /*
+   * The given `frame` is about to be popped; `completion` explains why.
+   *
+   * When this method returns true, it must set `resumeMode` and `vp` to a
+   * resumption value specifying how execution should continue.
+   *
+   * When this method returns false, it should set an exception on `cx`.
+   */
+  virtual bool onPop(JSContext* cx, HandleDebuggerFrame frame,
+                     const Completion& completion, ResumeMode& resumeMode,
+                     MutableHandleValue vp) = 0;
+};
+
+class ScriptedOnPopHandler final : public OnPopHandler {
+ public:
+  explicit ScriptedOnPopHandler(JSObject* object);
+  virtual JSObject* object() const override;
+  virtual void hold(JSObject* owner) override;
+  virtual void drop(JSFreeOp* fop, JSObject* owner) override;
+  virtual void trace(JSTracer* tracer) override;
+  virtual size_t allocSize() const override;
+  virtual bool onPop(JSContext* cx, HandleDebuggerFrame frame,
+                     const Completion& completion, ResumeMode& resumeMode,
+                     MutableHandleValue vp) override;
+
+ private:
+  const HeapPtr<JSObject*> object_;
+};
+
+enum class DebuggerFrameType { Eval, Global, Call, Module, WasmCall };
+
+enum class DebuggerFrameImplementation { Interpreter, Baseline, Ion, Wasm };
+
+class DebuggerArguments : public NativeObject {
+ public:
+  static const JSClass class_;
+
+  static DebuggerArguments* create(JSContext* cx, HandleObject proto,
+                                   HandleDebuggerFrame frame);
+
+ private:
+  enum { FRAME_SLOT };
+
+  static const unsigned RESERVED_SLOTS = 1;
+};
+
+class DebuggerFrame : public NativeObject {
+  friend class DebuggerArguments;
+  friend class ScriptedOnStepHandler;
+  friend class ScriptedOnPopHandler;
+
+ public:
+  static const JSClass class_;
+
+  enum {
+    OWNER_SLOT = 0,
+    ARGUMENTS_SLOT,
+    ONSTEP_HANDLER_SLOT,
+    ONPOP_HANDLER_SLOT,
+
+    // If this is a frame for a generator call, and the generator object has
+    // been created (which doesn't happen until after default argument
+    // evaluation and destructuring), then this is a PrivateValue pointing to a
+    // GeneratorInfo struct that points to the call's AbstractGeneratorObject.
+    // This allows us to implement Debugger.Frame methods even while the call is
+    // suspended, and we have no FrameIter::Data.
+    //
+    // While Debugger::generatorFrames maps an AbstractGeneratorObject to its
+    // Debugger.Frame, this link represents the reverse relation, from a
+    // Debugger.Frame to its generator object. This slot is set if and only if
+    // there is a corresponding entry in generatorFrames.
+    GENERATOR_INFO_SLOT,
+
+    RESERVED_SLOTS,
+  };
+
+  void trace(JSTracer* trc);
+
+  static NativeObject* initClass(JSContext* cx, Handle<GlobalObject*> global,
+                                 HandleObject dbgCtor);
+  static DebuggerFrame* create(JSContext* cx, HandleObject proto,
+                               HandleNativeObject debugger,
+                               const FrameIter* maybeIter,
+                               Handle<AbstractGeneratorObject*> maybeGenerator);
+
+  static MOZ_MUST_USE bool getArguments(JSContext* cx,
+                                        HandleDebuggerFrame frame,
+                                        MutableHandleDebuggerArguments result);
+  static MOZ_MUST_USE bool getCallee(JSContext* cx, HandleDebuggerFrame frame,
+                                     MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getIsConstructing(JSContext* cx,
+                                             HandleDebuggerFrame frame,
+                                             bool& result);
+  static MOZ_MUST_USE bool getEnvironment(
+      JSContext* cx, HandleDebuggerFrame frame,
+      MutableHandleDebuggerEnvironment result);
+  static MOZ_MUST_USE bool getOffset(JSContext* cx, HandleDebuggerFrame frame,
+                                     size_t& result);
+  static MOZ_MUST_USE bool getOlder(JSContext* cx, HandleDebuggerFrame frame,
+                                    MutableHandleDebuggerFrame result);
+  static MOZ_MUST_USE bool getAsyncPromise(JSContext* cx,
+                                           HandleDebuggerFrame frame,
+                                           MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getOlderSavedFrame(JSContext* cx,
+                                              HandleDebuggerFrame frame,
+                                              MutableHandleSavedFrame result);
+  static MOZ_MUST_USE bool getThis(JSContext* cx, HandleDebuggerFrame frame,
+                                   MutableHandleValue result);
+  static DebuggerFrameType getType(HandleDebuggerFrame frame);
+  static DebuggerFrameImplementation getImplementation(
+      HandleDebuggerFrame frame);
+  static MOZ_MUST_USE bool setOnStepHandler(JSContext* cx,
+                                            HandleDebuggerFrame frame,
+                                            OnStepHandler* handler);
+
+  static MOZ_MUST_USE JS::Result<Completion> eval(
+      JSContext* cx, HandleDebuggerFrame frame,
+      mozilla::Range<const char16_t> chars, HandleObject bindings,
+      const EvalOptions& options);
+
+  static MOZ_MUST_USE DebuggerFrame* check(JSContext* cx, HandleValue thisv);
+
+  bool isOnStack() const;
+
+  // Like isOnStack, but works even in the midst of a relocating GC.
+  bool isOnStackMaybeForwarded() const;
+
+  bool isSuspended() const;
+
+  OnStepHandler* onStepHandler() const;
+  OnPopHandler* onPopHandler() const;
+  void setOnPopHandler(JSContext* cx, OnPopHandler* handler);
+
+  inline bool hasGeneratorInfo() const;
+
+  // If hasGeneratorInfo(), return an direct cross-compartment reference to this
+  // Debugger.Frame's generator object.
+  AbstractGeneratorObject& unwrappedGenerator() const;
+
+#ifdef DEBUG
+  JSScript* generatorScript() const;
+#endif
+
+  /*
+   * Associate the generator object genObj with this Debugger.Frame. This
+   * association allows the Debugger.Frame to track the generator's execution
+   * across suspensions and resumptions, and to implement some methods even
+   * while the generator is suspended.
+   *
+   * The context `cx` must be in the Debugger.Frame's realm, and `genObj` must
+   * be in a debuggee realm.
+   *
+   * Technically, the generator activation need not actually be on the stack
+   * right now; it's okay to call this method on a Debugger.Frame that has no
+   * ScriptFrameIter::Data at present. However, this function has no way to
+   * verify that genObj really is the generator associated with the call for
+   * which this Debugger.Frame was originally created, so it's best to make the
+   * association while the call is on the stack, and the relationships are easy
+   * to discern.
+   */
+  MOZ_MUST_USE bool setGeneratorInfo(JSContext* cx,
+                                     Handle<AbstractGeneratorObject*> genObj);
+
+  /*
+   * Undo the effects of a prior call to setGenerator.
+   *
+   * If provided, owner must be the Debugger to which this Debugger.Frame
+   * belongs; remove this frame's entry from its generatorFrames map, and clean
+   * up its cross-compartment wrapper table entry. The owner must be passed
+   * unless this method is being called from the Debugger.Frame's finalizer. (In
+   * that case, the owner is not reliably available, and is not actually
+   * necessary.)
+   *
+   * If maybeGeneratorFramesEnum is non-null, use it to remove this frame's
+   * entry from the Debugger's generatorFrames weak map. In this case, this
+   * function will not otherwise disturb generatorFrames. Passing the enum
+   * allows this function to be used while iterating over generatorFrames.
+   */
+  void clearGeneratorInfo(JSFreeOp* fop);
+
+  /*
+   * Called after a generator/async frame is resumed, before exposing this
+   * Debugger.Frame object to any hooks.
+   */
+  bool resume(const FrameIter& iter);
+
+  bool hasAnyHooks() const;
+
+  bool isInstance() const;
+  Debugger* owner() const;
+
+ private:
+  static const JSClassOps classOps_;
+
+  static const JSPropertySpec properties_[];
+  static const JSFunctionSpec methods_[];
+
+  static void finalize(JSFreeOp* fop, JSObject* obj);
+
+  static AbstractFramePtr getReferent(HandleDebuggerFrame frame);
+  static MOZ_MUST_USE bool requireScriptReferent(JSContext* cx,
+                                                 HandleDebuggerFrame frame);
+
+  static MOZ_MUST_USE bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+
+  MOZ_MUST_USE bool incrementStepperCounter(JSContext* cx,
+                                            AbstractFramePtr referent);
+  MOZ_MUST_USE bool incrementStepperCounter(JSContext* cx, JSScript* script);
+  void decrementStepperCounter(JSFreeOp* fop, JSScript* script);
+  void decrementStepperCounter(JSFreeOp* fop, AbstractFramePtr referent);
+
+  FrameIter::Data* frameIterData() const;
+  void setFrameIterData(FrameIter::Data*);
+  void freeFrameIterData(JSFreeOp* fop);
+
+ public:
+  FrameIter getFrameIter(JSContext* cx);
+
+  void terminate(JSFreeOp* fop, AbstractFramePtr frame);
+  void suspend(JSFreeOp* fop);
+
+  MOZ_MUST_USE bool replaceFrameIterData(JSContext* cx, const FrameIter&);
+
+  class GeneratorInfo;
+  inline GeneratorInfo* generatorInfo() const;
+};
+
+} /* namespace js */
+
+#endif /* debugger_Frame_h */
diff --git a/js/src/debugger/NoExecute.cpp b/js/src/debugger/NoExecute.cpp
new file mode 100644
index 0000000000..de18225a1a
--- /dev/null
+++ b/js/src/debugger/NoExecute.cpp
@@ -0,0 +1,91 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/NoExecute.h"
+
+#include "mozilla/Sprintf.h"  // for SprintfLiteral
+
+#include <stdio.h>  // for fprintf, stdout
+
+#include "jsapi.h"  // for Handle
+
+#include "debugger/Debugger.h"        // for Debugger
+#include "js/friend/DumpFunctions.h"  // for DumpBacktrace
+#include "js/friend/ErrorMessages.h"  // for GetErrorMessage, JSMSG_DEBUGGEE_WOULD_RUN
+#include "js/Promise.h"               // for AutoDebuggerJobQueueInterruption
+#include "vm/JSContext.h"             // for ProtectedDataContextArg, JSContext
+#include "vm/JSScript.h"              // for JSScript
+#include "vm/Realm.h"                 // for AutoRealm, Realm
+#include "vm/Warnings.h"              // for WarnNumberLatin1
+
+#include "vm/Realm-inl.h"  // for AutoRealm::AutoRealm
+
+using namespace js;
+
+EnterDebuggeeNoExecute::EnterDebuggeeNoExecute(
+    JSContext* cx, Debugger& dbg,
+    const JS::AutoDebuggerJobQueueInterruption& adjqiProof)
+    : dbg_(dbg), unlocked_(nullptr), reported_(false) {
+  MOZ_ASSERT(adjqiProof.initialized());
+  stack_ = &cx->noExecuteDebuggerTop.ref();
+  prev_ = *stack_;
+  *stack_ = this;
+}
+
+#ifdef DEBUG
+/* static */
+bool EnterDebuggeeNoExecute::isLockedInStack(JSContext* cx, Debugger& dbg) {
+  for (EnterDebuggeeNoExecute* it = cx->noExecuteDebuggerTop; it;
+       it = it->prev_) {
+    if (&it->debugger() == &dbg) {
+      return !it->unlocked_;
+    }
+  }
+  return false;
+}
+#endif
+
+/* static */
+EnterDebuggeeNoExecute* EnterDebuggeeNoExecute::findInStack(JSContext* cx) {
+  Realm* debuggee = cx->realm();
+  for (EnterDebuggeeNoExecute* it = cx->noExecuteDebuggerTop; it;
+       it = it->prev_) {
+    Debugger& dbg = it->debugger();
+    if (!it->unlocked_ && dbg.observesGlobal(debuggee->maybeGlobal())) {
+      return it;
+    }
+  }
+  return nullptr;
+}
+
+/* static */
+bool EnterDebuggeeNoExecute::reportIfFoundInStack(JSContext* cx,
+                                                  HandleScript script) {
+  if (EnterDebuggeeNoExecute* nx = findInStack(cx)) {
+    bool warning = !cx->options().throwOnDebuggeeWouldRun();
+    if (!warning || !nx->reported_) {
+      AutoRealm ar(cx, nx->debugger().toJSObject());
+      nx->reported_ = true;
+      if (cx->options().dumpStackOnDebuggeeWouldRun()) {
+        fprintf(stdout, "Dumping stack for DebuggeeWouldRun:\n");
+        DumpBacktrace(cx);
+      }
+      const char* filename = script->filename() ? script->filename() : "(none)";
+      char linenoStr[15];
+      SprintfLiteral(linenoStr, "%u", script->lineno());
+      // FIXME: filename should be UTF-8 (bug 987069).
+      if (warning) {
+        return WarnNumberLatin1(cx, JSMSG_DEBUGGEE_WOULD_RUN, filename,
+                                linenoStr);
+      }
+
+      JS_ReportErrorNumberLatin1(cx, GetErrorMessage, nullptr,
+                                 JSMSG_DEBUGGEE_WOULD_RUN, filename, linenoStr);
+      return false;
+    }
+  }
+  return true;
+}
diff --git a/js/src/debugger/NoExecute.h b/js/src/debugger/NoExecute.h
new file mode 100644
index 0000000000..49278eacf6
--- /dev/null
+++ b/js/src/debugger/NoExecute.h
@@ -0,0 +1,96 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_NoExecute_h
+#define debugger_NoExecute_h
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+#include "mozilla/Attributes.h"  // for MOZ_RAII
+
+#include "jsapi.h"
+
+#include "NamespaceImports.h"  // for HandleScript
+#include "js/Promise.h"        // for JS::AutoDebuggerJobQueueInterruption
+
+namespace js {
+
+class Debugger;
+class LeaveDebuggeeNoExecute;
+
+// Prevents all the debuggeee compartments of a given Debugger from executing
+// scripts. Attempts to run script will throw an
+// instance of Debugger.DebuggeeWouldRun from the topmost locked Debugger's
+// compartment.
+class MOZ_RAII EnterDebuggeeNoExecute {
+  friend class LeaveDebuggeeNoExecute;
+
+  Debugger& dbg_;
+  EnterDebuggeeNoExecute** stack_;
+  EnterDebuggeeNoExecute* prev_;
+
+  // Non-nullptr when unlocked temporarily by a LeaveDebuggeeNoExecute.
+  LeaveDebuggeeNoExecute* unlocked_;
+
+  // When DebuggeeWouldRun is a warning instead of an error, whether we've
+  // reported a warning already.
+  bool reported_;
+
+ public:
+  // Mark execution in dbg's debuggees as forbidden, for the lifetime of this
+  // object. Require an AutoDebuggerJobQueueInterruption in scope.
+  explicit EnterDebuggeeNoExecute(
+      JSContext* cx, Debugger& dbg,
+      const JS::AutoDebuggerJobQueueInterruption& adjqiProof);
+
+  ~EnterDebuggeeNoExecute() {
+    MOZ_ASSERT(*stack_ == this);
+    *stack_ = prev_;
+  }
+
+  Debugger& debugger() const { return dbg_; }
+
+#ifdef DEBUG
+  static bool isLockedInStack(JSContext* cx, Debugger& dbg);
+#endif
+
+  // Given a JSContext entered into a debuggee realm, find the lock
+  // that locks it. Returns nullptr if not found.
+  static EnterDebuggeeNoExecute* findInStack(JSContext* cx);
+
+  // Given a JSContext entered into a debuggee compartment, report a
+  // warning or an error if there is a lock that locks it.
+  static bool reportIfFoundInStack(JSContext* cx, HandleScript script);
+};
+
+// Given a JSContext entered into a debuggee compartment, if it is in
+// an NX section, unlock the topmost EnterDebuggeeNoExecute instance.
+//
+// Does nothing if debuggee is not in an NX section. For example, this
+// situation arises when invocation functions are called without entering
+// Debugger code, e.g., calling D.O.p.executeInGlobal or D.O.p.apply.
+class MOZ_RAII LeaveDebuggeeNoExecute {
+  EnterDebuggeeNoExecute* prevLocked_;
+
+ public:
+  explicit LeaveDebuggeeNoExecute(JSContext* cx)
+      : prevLocked_(EnterDebuggeeNoExecute::findInStack(cx)) {
+    if (prevLocked_) {
+      MOZ_ASSERT(!prevLocked_->unlocked_);
+      prevLocked_->unlocked_ = this;
+    }
+  }
+
+  ~LeaveDebuggeeNoExecute() {
+    if (prevLocked_) {
+      MOZ_ASSERT(prevLocked_->unlocked_ == this);
+      prevLocked_->unlocked_ = nullptr;
+    }
+  }
+};
+
+} /* namespace js */
+
+#endif /* debugger_NoExecute_h */
diff --git a/js/src/debugger/Object-inl.h b/js/src/debugger/Object-inl.h
new file mode 100644
index 0000000000..890a426f83
--- /dev/null
+++ b/js/src/debugger/Object-inl.h
@@ -0,0 +1,49 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Object_inl_h
+#define debugger_Object_inl_h
+
+#include "debugger/Object.h"  // for DebuggerObject
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+
+#include "NamespaceImports.h"  // for Value
+
+#include "debugger/Debugger.h"  // for Debugger
+#include "js/Wrapper.h"         // for CheckedUnwrapStatic
+#include "vm/JSObject.h"        // for JSObject
+#include "vm/PromiseObject.h"   // for js::PromiseObject
+
+#include "debugger/Debugger-inl.h"  // for Debugger::fromJSObject
+
+// The Debugger.Object.prototype object also has a class of
+// DebuggerObject::class_ so we differentiate instances from the prototype
+// based on the presence of an owner debugger.
+inline bool js::DebuggerObject::isInstance() const {
+  return !getReservedSlot(OWNER_SLOT).isUndefined();
+}
+
+inline js::Debugger* js::DebuggerObject::owner() const {
+  MOZ_ASSERT(isInstance());
+  JSObject* dbgobj = &getReservedSlot(OWNER_SLOT).toObject();
+  return Debugger::fromJSObject(dbgobj);
+}
+
+inline js::PromiseObject* js::DebuggerObject::promise() const {
+  MOZ_ASSERT(isPromise());
+
+  JSObject* referent = this->referent();
+  if (IsCrossCompartmentWrapper(referent)) {
+    // We know we have a Promise here, so CheckedUnwrapStatic is fine.
+    referent = CheckedUnwrapStatic(referent);
+    MOZ_ASSERT(referent);
+  }
+
+  return &referent->as<PromiseObject>();
+}
+
+#endif /* debugger_Object_inl_h */
diff --git a/js/src/debugger/Object.cpp b/js/src/debugger/Object.cpp
new file mode 100644
index 0000000000..5675b63ad8
--- /dev/null
+++ b/js/src/debugger/Object.cpp
@@ -0,0 +1,2671 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Object-inl.h"
+
+#include "mozilla/Maybe.h"   // for Maybe, Nothing, Some
+#include "mozilla/Range.h"   // for Range
+#include "mozilla/Result.h"  // for Result
+#include "mozilla/Vector.h"  // for Vector
+
+#include <algorithm>
+#include <string.h>     // for size_t, strlen
+#include <type_traits>  // for remove_reference<>::type
+#include <utility>      // for move
+
+#include "jsapi.h"  // for CallArgs, RootedObject, Rooted
+
+#include "builtin/Array.h"       // for NewDenseCopiedArray
+#include "builtin/Promise.h"     // for PromiseReactionRecordBuilder
+#include "debugger/Debugger.h"   // for Completion, Debugger
+#include "debugger/Frame.h"      // for DebuggerFrame
+#include "debugger/NoExecute.h"  // for LeaveDebuggeeNoExecute
+#include "debugger/Script.h"     // for DebuggerScript
+#include "debugger/Source.h"     // for DebuggerSource
+#include "gc/Barrier.h"          // for ImmutablePropertyNamePtr
+#include "gc/Rooting.h"          // for RootedDebuggerObject
+#include "gc/Tracer.h"  // for TraceManuallyBarrieredCrossCompartmentEdge
+#include "js/CompilationAndEvaluation.h"  //  for Compile
+#include "js/Conversions.h"               // for ToObject
+#include "js/friend/ErrorMessages.h"      // for GetErrorMessage, JSMSG_*
+#include "js/friend/WindowProxy.h"  // for IsWindow, IsWindowProxy, ToWindowIfWindowProxy
+#include "js/HeapAPI.h"             // for IsInsideNursery
+#include "js/Promise.h"             // for PromiseState
+#include "js/Proxy.h"               // for PropertyDescriptor
+#include "js/SourceText.h"               // for SourceText
+#include "js/StableStringChars.h"        // for AutoStableStringChars
+#include "js/String.h"                   // for JS::StringHasLatin1Chars
+#include "proxy/ScriptedProxyHandler.h"  // for ScriptedProxyHandler
+#include "vm/ArgumentsObject.h"          // for ARGS_LENGTH_MAX
+#include "vm/ArrayObject.h"              // for ArrayObject
+#include "vm/AsyncFunction.h"            // for AsyncGeneratorObject
+#include "vm/AsyncIteration.h"           // for AsyncFunctionGeneratorObject
+#include "vm/BytecodeUtil.h"             // for JSDVG_SEARCH_STACK
+#include "vm/Compartment.h"              // for Compartment
+#include "vm/EnvironmentObject.h"        // for GetDebugEnvironmentForFunction
+#include "vm/ErrorObject.h"              // for JSObject::is, ErrorObject
+#include "vm/GeneratorObject.h"          // for AbstractGeneratorObject
+#include "vm/GlobalObject.h"             // for JSObject::is, GlobalObject
+#include "vm/Instrumentation.h"          // for RealmInstrumentation
+#include "vm/Interpreter.h"              // for Call
+#include "vm/JSAtom.h"                   // for Atomize, js_apply_str
+#include "vm/JSContext.h"                // for JSContext, ReportValueError
+#include "vm/JSFunction.h"               // for JSFunction
+#include "vm/JSScript.h"                 // for JSScript
+#include "vm/NativeObject.h"             // for NativeObject, JSObject::is
+#include "vm/ObjectGroup.h"              // for GenericObject, NewObjectKind
+#include "vm/ObjectOperations.h"         // for DefineProperty
+#include "vm/PlainObject.h"              // for js::PlainObject
+#include "vm/PromiseObject.h"            // for js::PromiseObject
+#include "vm/Realm.h"                    // for AutoRealm, ErrorCopier, Realm
+#include "vm/Runtime.h"                  // for JSAtomState
+#include "vm/SavedFrame.h"               // for SavedFrame
+#include "vm/Scope.h"                    // for PositionalFormalParameterIter
+#include "vm/SelfHosting.h"              // for GetClonedSelfHostedFunctionName
+#include "vm/Shape.h"                    // for Shape
+#include "vm/Stack.h"                    // for InvokeArgs
+#include "vm/StringType.h"               // for JSAtom, PropertyName
+#include "vm/WrapperObject.h"            // for JSObject::is, WrapperObject
+
+#include "vm/Compartment-inl.h"  // for Compartment::wrap
+#include "vm/JSObject-inl.h"  // for GetObjectClassName, InitClass, NewObjectWithGivenProtoAndKind, ToPropertyKey
+#include "vm/NativeObject-inl.h"      // for NativeObject::global
+#include "vm/ObjectOperations-inl.h"  // for DeleteProperty, GetProperty
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+
+using namespace js;
+
+using JS::AutoStableStringChars;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+
+const JSClassOps DebuggerObject::classOps_ = {
+    nullptr,                          // addProperty
+    nullptr,                          // delProperty
+    nullptr,                          // enumerate
+    nullptr,                          // newEnumerate
+    nullptr,                          // resolve
+    nullptr,                          // mayResolve
+    nullptr,                          // finalize
+    nullptr,                          // call
+    nullptr,                          // hasInstance
+    nullptr,                          // construct
+    CallTraceMethod<DebuggerObject>,  // trace
+};
+
+const JSClass DebuggerObject::class_ = {
+    "Object", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS),
+    &classOps_};
+
+void DebuggerObject::trace(JSTracer* trc) {
+  // There is a barrier on private pointers, so the Unbarriered marking
+  // is okay.
+  if (JSObject* referent = (JSObject*)getPrivate()) {
+    TraceManuallyBarrieredCrossCompartmentEdge(
+        trc, static_cast<JSObject*>(this), &referent,
+        "Debugger.Object referent");
+    setPrivateUnbarriered(referent);
+  }
+}
+
+static DebuggerObject* DebuggerObject_checkThis(JSContext* cx,
+                                                const CallArgs& args) {
+  JSObject* thisobj = RequireObject(cx, args.thisv());
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Object",
+                              "method", thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  // Forbid Debugger.Object.prototype, which is of class DebuggerObject::class_
+  // but isn't a real working Debugger.Object.
+  DebuggerObject* nthisobj = &thisobj->as<DebuggerObject>();
+  if (!nthisobj->isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Object",
+                              "method", "prototype object");
+    return nullptr;
+  }
+  return nthisobj;
+}
+
+/* static */
+bool DebuggerObject::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Object");
+  return false;
+}
+
+struct MOZ_STACK_CLASS DebuggerObject::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  HandleDebuggerObject object;
+  RootedObject referent;
+
+  CallData(JSContext* cx, const CallArgs& args, HandleDebuggerObject obj)
+      : cx(cx), args(args), object(obj), referent(cx, obj->referent()) {}
+
+  // JSNative properties
+  bool callableGetter();
+  bool isBoundFunctionGetter();
+  bool isArrowFunctionGetter();
+  bool isAsyncFunctionGetter();
+  bool isClassConstructorGetter();
+  bool isGeneratorFunctionGetter();
+  bool protoGetter();
+  bool classGetter();
+  bool nameGetter();
+  bool displayNameGetter();
+  bool parameterNamesGetter();
+  bool scriptGetter();
+  bool environmentGetter();
+  bool boundTargetFunctionGetter();
+  bool boundThisGetter();
+  bool boundArgumentsGetter();
+  bool allocationSiteGetter();
+  bool isErrorGetter();
+  bool errorMessageNameGetter();
+  bool errorNotesGetter();
+  bool errorLineNumberGetter();
+  bool errorColumnNumberGetter();
+  bool isProxyGetter();
+  bool proxyTargetGetter();
+  bool proxyHandlerGetter();
+  bool isPromiseGetter();
+  bool promiseStateGetter();
+  bool promiseValueGetter();
+  bool promiseReasonGetter();
+  bool promiseLifetimeGetter();
+  bool promiseTimeToResolutionGetter();
+  bool promiseAllocationSiteGetter();
+  bool promiseResolutionSiteGetter();
+  bool promiseIDGetter();
+  bool promiseDependentPromisesGetter();
+
+  // JSNative methods
+  bool isExtensibleMethod();
+  bool isSealedMethod();
+  bool isFrozenMethod();
+  bool getPropertyMethod();
+  bool setPropertyMethod();
+  bool getOwnPropertyNamesMethod();
+  bool getOwnPropertySymbolsMethod();
+  bool getOwnPropertyDescriptorMethod();
+  bool preventExtensionsMethod();
+  bool sealMethod();
+  bool freezeMethod();
+  bool definePropertyMethod();
+  bool definePropertiesMethod();
+  bool deletePropertyMethod();
+  bool callMethod();
+  bool applyMethod();
+  bool asEnvironmentMethod();
+  bool forceLexicalInitializationByNameMethod();
+  bool executeInGlobalMethod();
+  bool executeInGlobalWithBindingsMethod();
+  bool createSource();
+  bool makeDebuggeeValueMethod();
+  bool makeDebuggeeNativeFunctionMethod();
+  bool isSameNativeMethod();
+  bool unsafeDereferenceMethod();
+  bool unwrapMethod();
+  bool setInstrumentationMethod();
+  bool setInstrumentationActiveMethod();
+  bool getPromiseReactionsMethod();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <DebuggerObject::CallData::Method MyMethod>
+/* static */
+bool DebuggerObject::CallData::ToNative(JSContext* cx, unsigned argc,
+                                        Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedDebuggerObject obj(cx, DebuggerObject_checkThis(cx, args));
+  if (!obj) {
+    return false;
+  }
+
+  CallData data(cx, args, obj);
+  return (data.*MyMethod)();
+}
+
+bool DebuggerObject::CallData::callableGetter() {
+  args.rval().setBoolean(object->isCallable());
+  return true;
+}
+
+bool DebuggerObject::CallData::isBoundFunctionGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  args.rval().setBoolean(object->isBoundFunction());
+  return true;
+}
+
+bool DebuggerObject::CallData::isArrowFunctionGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  args.rval().setBoolean(object->isArrowFunction());
+  return true;
+}
+
+bool DebuggerObject::CallData::isAsyncFunctionGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  args.rval().setBoolean(object->isAsyncFunction());
+  return true;
+}
+
+bool DebuggerObject::CallData::isGeneratorFunctionGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  args.rval().setBoolean(object->isGeneratorFunction());
+  return true;
+}
+
+bool DebuggerObject::CallData::isClassConstructorGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  args.rval().setBoolean(object->isClassConstructor());
+  return true;
+}
+
+bool DebuggerObject::CallData::protoGetter() {
+  RootedDebuggerObject result(cx);
+  if (!DebuggerObject::getPrototypeOf(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::classGetter() {
+  RootedString result(cx);
+  if (!DebuggerObject::getClassName(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setString(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::nameGetter() {
+  if (!object->isFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedString result(cx, object->name(cx));
+  if (result) {
+    args.rval().setString(result);
+  } else {
+    args.rval().setUndefined();
+  }
+  return true;
+}
+
+bool DebuggerObject::CallData::displayNameGetter() {
+  if (!object->isFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedString result(cx, object->displayName(cx));
+  if (result) {
+    args.rval().setString(result);
+  } else {
+    args.rval().setUndefined();
+  }
+  return true;
+}
+
+bool DebuggerObject::CallData::parameterNamesGetter() {
+  if (!object->isDebuggeeFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedFunction referent(cx, &object->referent()->as<JSFunction>());
+
+  ArrayObject* arr = GetFunctionParameterNamesArray(cx, referent);
+  if (!arr) {
+    return false;
+  }
+
+  args.rval().setObject(*arr);
+  return true;
+}
+
+bool DebuggerObject::CallData::scriptGetter() {
+  Debugger* dbg = object->owner();
+
+  if (!referent->is<JSFunction>()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedFunction fun(cx, &referent->as<JSFunction>());
+  if (!IsInterpretedNonSelfHostedFunction(fun)) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedScript script(cx, GetOrCreateFunctionScript(cx, fun));
+  if (!script) {
+    return false;
+  }
+
+  // Only hand out debuggee scripts.
+  if (!dbg->observesScript(script)) {
+    args.rval().setNull();
+    return true;
+  }
+
+  RootedDebuggerScript scriptObject(cx, dbg->wrapScript(cx, script));
+  if (!scriptObject) {
+    return false;
+  }
+
+  args.rval().setObject(*scriptObject);
+  return true;
+}
+
+bool DebuggerObject::CallData::environmentGetter() {
+  Debugger* dbg = object->owner();
+
+  // Don't bother switching compartments just to check obj's type and get its
+  // env.
+  if (!referent->is<JSFunction>()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedFunction fun(cx, &referent->as<JSFunction>());
+  if (!IsInterpretedNonSelfHostedFunction(fun)) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  // Only hand out environments of debuggee functions.
+  if (!dbg->observesGlobal(&fun->global())) {
+    args.rval().setNull();
+    return true;
+  }
+
+  Rooted<Env*> env(cx);
+  {
+    AutoRealm ar(cx, fun);
+    env = GetDebugEnvironmentForFunction(cx, fun);
+    if (!env) {
+      return false;
+    }
+  }
+
+  return dbg->wrapEnvironment(cx, env, args.rval());
+}
+
+bool DebuggerObject::CallData::boundTargetFunctionGetter() {
+  if (!object->isDebuggeeFunction() || !object->isBoundFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedDebuggerObject result(cx);
+  if (!DebuggerObject::getBoundTargetFunction(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerObject::CallData::boundThisGetter() {
+  if (!object->isDebuggeeFunction() || !object->isBoundFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  return DebuggerObject::getBoundThis(cx, object, args.rval());
+}
+
+bool DebuggerObject::CallData::boundArgumentsGetter() {
+  if (!object->isDebuggeeFunction() || !object->isBoundFunction()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  Rooted<ValueVector> result(cx, ValueVector(cx));
+  if (!DebuggerObject::getBoundArguments(cx, object, &result)) {
+    return false;
+  }
+
+  RootedObject obj(cx,
+                   NewDenseCopiedArray(cx, result.length(), result.begin()));
+  if (!obj) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+bool DebuggerObject::CallData::allocationSiteGetter() {
+  RootedObject result(cx);
+  if (!DebuggerObject::getAllocationSite(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+// Returns the "name" field (see js/public/friend/ErrorNumbers.msg), which may
+// be used as a unique identifier, for any error object with a JSErrorReport or
+// undefined if the object has no JSErrorReport.
+bool DebuggerObject::CallData::errorMessageNameGetter() {
+  RootedString result(cx);
+  if (!DebuggerObject::getErrorMessageName(cx, object, &result)) {
+    return false;
+  }
+
+  if (result) {
+    args.rval().setString(result);
+  } else {
+    args.rval().setUndefined();
+  }
+  return true;
+}
+
+bool DebuggerObject::CallData::isErrorGetter() {
+  args.rval().setBoolean(object->isError());
+  return true;
+}
+
+bool DebuggerObject::CallData::errorNotesGetter() {
+  return DebuggerObject::getErrorNotes(cx, object, args.rval());
+}
+
+bool DebuggerObject::CallData::errorLineNumberGetter() {
+  return DebuggerObject::getErrorLineNumber(cx, object, args.rval());
+}
+
+bool DebuggerObject::CallData::errorColumnNumberGetter() {
+  return DebuggerObject::getErrorColumnNumber(cx, object, args.rval());
+}
+
+bool DebuggerObject::CallData::isProxyGetter() {
+  args.rval().setBoolean(object->isScriptedProxy());
+  return true;
+}
+
+bool DebuggerObject::CallData::proxyTargetGetter() {
+  if (!object->isScriptedProxy()) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  Rooted<DebuggerObject*> result(cx);
+  if (!DebuggerObject::getScriptedProxyTarget(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::proxyHandlerGetter() {
+  if (!object->isScriptedProxy()) {
+    args.rval().setUndefined();
+    return true;
+  }
+  Rooted<DebuggerObject*> result(cx);
+  if (!DebuggerObject::getScriptedProxyHandler(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::isPromiseGetter() {
+  args.rval().setBoolean(object->isPromise());
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseStateGetter() {
+  if (!DebuggerObject::requirePromise(cx, object)) {
+    return false;
+  }
+
+  RootedValue result(cx);
+  switch (object->promiseState()) {
+    case JS::PromiseState::Pending:
+      result.setString(cx->names().pending);
+      break;
+    case JS::PromiseState::Fulfilled:
+      result.setString(cx->names().fulfilled);
+      break;
+    case JS::PromiseState::Rejected:
+      result.setString(cx->names().rejected);
+      break;
+  }
+
+  args.rval().set(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseValueGetter() {
+  if (!DebuggerObject::requirePromise(cx, object)) {
+    return false;
+  }
+
+  if (object->promiseState() != JS::PromiseState::Fulfilled) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_PROMISE_NOT_FULFILLED);
+    return false;
+  }
+
+  return DebuggerObject::getPromiseValue(cx, object, args.rval());
+  ;
+}
+
+bool DebuggerObject::CallData::promiseReasonGetter() {
+  if (!DebuggerObject::requirePromise(cx, object)) {
+    return false;
+  }
+
+  if (object->promiseState() != JS::PromiseState::Rejected) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_PROMISE_NOT_REJECTED);
+    return false;
+  }
+
+  return DebuggerObject::getPromiseReason(cx, object, args.rval());
+}
+
+bool DebuggerObject::CallData::promiseLifetimeGetter() {
+  if (!DebuggerObject::requirePromise(cx, object)) {
+    return false;
+  }
+
+  args.rval().setNumber(object->promiseLifetime());
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseTimeToResolutionGetter() {
+  if (!DebuggerObject::requirePromise(cx, object)) {
+    return false;
+  }
+
+  if (object->promiseState() == JS::PromiseState::Pending) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_PROMISE_NOT_RESOLVED);
+    return false;
+  }
+
+  args.rval().setNumber(object->promiseTimeToResolution());
+  return true;
+}
+
+static PromiseObject* EnsurePromise(JSContext* cx, HandleObject referent) {
+  // We only care about promises, so CheckedUnwrapStatic is OK.
+  RootedObject obj(cx, CheckedUnwrapStatic(referent));
+  if (!obj) {
+    ReportAccessDenied(cx);
+    return nullptr;
+  }
+  if (!obj->is<PromiseObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_EXPECTED_TYPE, "Debugger", "Promise",
+                              obj->getClass()->name);
+    return nullptr;
+  }
+  return &obj->as<PromiseObject>();
+}
+
+bool DebuggerObject::CallData::promiseAllocationSiteGetter() {
+  Rooted<PromiseObject*> promise(cx, EnsurePromise(cx, referent));
+  if (!promise) {
+    return false;
+  }
+
+  RootedObject allocSite(cx, promise->allocationSite());
+  if (!allocSite) {
+    args.rval().setNull();
+    return true;
+  }
+
+  if (!cx->compartment()->wrap(cx, &allocSite)) {
+    return false;
+  }
+  args.rval().set(ObjectValue(*allocSite));
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseResolutionSiteGetter() {
+  Rooted<PromiseObject*> promise(cx, EnsurePromise(cx, referent));
+  if (!promise) {
+    return false;
+  }
+
+  if (promise->state() == JS::PromiseState::Pending) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_PROMISE_NOT_RESOLVED);
+    return false;
+  }
+
+  RootedObject resolutionSite(cx, promise->resolutionSite());
+  if (!resolutionSite) {
+    args.rval().setNull();
+    return true;
+  }
+
+  if (!cx->compartment()->wrap(cx, &resolutionSite)) {
+    return false;
+  }
+  args.rval().set(ObjectValue(*resolutionSite));
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseIDGetter() {
+  Rooted<PromiseObject*> promise(cx, EnsurePromise(cx, referent));
+  if (!promise) {
+    return false;
+  }
+
+  args.rval().setNumber(double(promise->getID()));
+  return true;
+}
+
+bool DebuggerObject::CallData::promiseDependentPromisesGetter() {
+  Debugger* dbg = object->owner();
+
+  Rooted<PromiseObject*> promise(cx, EnsurePromise(cx, referent));
+  if (!promise) {
+    return false;
+  }
+
+  Rooted<GCVector<Value>> values(cx, GCVector<Value>(cx));
+  {
+    JSAutoRealm ar(cx, promise);
+    if (!promise->dependentPromises(cx, &values)) {
+      return false;
+    }
+  }
+  for (size_t i = 0; i < values.length(); i++) {
+    if (!dbg->wrapDebuggeeValue(cx, values[i])) {
+      return false;
+    }
+  }
+  RootedArrayObject promises(cx);
+  if (values.length() == 0) {
+    promises = NewDenseEmptyArray(cx);
+  } else {
+    promises = NewDenseCopiedArray(cx, values.length(), values[0].address());
+  }
+  if (!promises) {
+    return false;
+  }
+  args.rval().setObject(*promises);
+  return true;
+}
+
+bool DebuggerObject::CallData::isExtensibleMethod() {
+  bool result;
+  if (!DebuggerObject::isExtensible(cx, object, result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::isSealedMethod() {
+  bool result;
+  if (!DebuggerObject::isSealed(cx, object, result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::isFrozenMethod() {
+  bool result;
+  if (!DebuggerObject::isFrozen(cx, object, result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::getOwnPropertyNamesMethod() {
+  Rooted<IdVector> ids(cx, IdVector(cx));
+  if (!DebuggerObject::getOwnPropertyNames(cx, object, &ids)) {
+    return false;
+  }
+
+  RootedObject obj(cx, IdVectorToArray(cx, ids));
+  if (!obj) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+bool DebuggerObject::CallData::getOwnPropertySymbolsMethod() {
+  Rooted<IdVector> ids(cx, IdVector(cx));
+  if (!DebuggerObject::getOwnPropertySymbols(cx, object, &ids)) {
+    return false;
+  }
+
+  RootedObject obj(cx, IdVectorToArray(cx, ids));
+  if (!obj) {
+    return false;
+  }
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
+bool DebuggerObject::CallData::getOwnPropertyDescriptorMethod() {
+  RootedId id(cx);
+  if (!ToPropertyKey(cx, args.get(0), &id)) {
+    return false;
+  }
+
+  Rooted<PropertyDescriptor> desc(cx);
+  if (!DebuggerObject::getOwnPropertyDescriptor(cx, object, id, &desc)) {
+    return false;
+  }
+
+  return JS::FromPropertyDescriptor(cx, desc, args.rval());
+}
+
+bool DebuggerObject::CallData::preventExtensionsMethod() {
+  if (!DebuggerObject::preventExtensions(cx, object)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerObject::CallData::sealMethod() {
+  if (!DebuggerObject::seal(cx, object)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerObject::CallData::freezeMethod() {
+  if (!DebuggerObject::freeze(cx, object)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerObject::CallData::definePropertyMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.defineProperty", 2)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  if (!ToPropertyKey(cx, args[0], &id)) {
+    return false;
+  }
+
+  Rooted<PropertyDescriptor> desc(cx);
+  if (!ToPropertyDescriptor(cx, args[1], false, &desc)) {
+    return false;
+  }
+
+  if (!DebuggerObject::defineProperty(cx, object, id, desc)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerObject::CallData::definePropertiesMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.defineProperties", 1)) {
+    return false;
+  }
+
+  RootedValue arg(cx, args[0]);
+  RootedObject props(cx, ToObject(cx, arg));
+  if (!props) {
+    return false;
+  }
+  RootedIdVector ids(cx);
+  Rooted<PropertyDescriptorVector> descs(cx, PropertyDescriptorVector(cx));
+  if (!ReadPropertyDescriptors(cx, props, false, &ids, &descs)) {
+    return false;
+  }
+  Rooted<IdVector> ids2(cx, IdVector(cx));
+  if (!ids2.append(ids.begin(), ids.end())) {
+    return false;
+  }
+
+  if (!DebuggerObject::defineProperties(cx, object, ids2, descs)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+/*
+ * This does a non-strict delete, as a matter of API design. The case where the
+ * property is non-configurable isn't necessarily exceptional here.
+ */
+bool DebuggerObject::CallData::deletePropertyMethod() {
+  RootedId id(cx);
+  if (!ToPropertyKey(cx, args.get(0), &id)) {
+    return false;
+  }
+
+  ObjectOpResult result;
+  if (!DebuggerObject::deleteProperty(cx, object, id, result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result.ok());
+  return true;
+}
+
+bool DebuggerObject::CallData::callMethod() {
+  RootedValue thisv(cx, args.get(0));
+
+  Rooted<ValueVector> nargs(cx, ValueVector(cx));
+  if (args.length() >= 2) {
+    if (!nargs.growBy(args.length() - 1)) {
+      return false;
+    }
+    for (size_t i = 1; i < args.length(); ++i) {
+      nargs[i - 1].set(args[i]);
+    }
+  }
+
+  Rooted<Maybe<Completion>> completion(
+      cx, DebuggerObject::call(cx, object, thisv, nargs));
+  if (!completion.get()) {
+    return false;
+  }
+
+  return completion->buildCompletionValue(cx, object->owner(), args.rval());
+}
+
+bool DebuggerObject::CallData::getPropertyMethod() {
+  Debugger* dbg = object->owner();
+
+  RootedId id(cx);
+  if (!ToPropertyKey(cx, args.get(0), &id)) {
+    return false;
+  }
+
+  RootedValue receiver(cx,
+                       args.length() < 2 ? ObjectValue(*object) : args.get(1));
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(cx, comp, getProperty(cx, object, id, receiver));
+  return comp.get().buildCompletionValue(cx, dbg, args.rval());
+}
+
+bool DebuggerObject::CallData::setPropertyMethod() {
+  Debugger* dbg = object->owner();
+
+  RootedId id(cx);
+  if (!ToPropertyKey(cx, args.get(0), &id)) {
+    return false;
+  }
+
+  RootedValue value(cx, args.get(1));
+
+  RootedValue receiver(cx,
+                       args.length() < 3 ? ObjectValue(*object) : args.get(2));
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(cx, comp,
+                             setProperty(cx, object, id, value, receiver));
+  return comp.get().buildCompletionValue(cx, dbg, args.rval());
+}
+
+bool DebuggerObject::CallData::applyMethod() {
+  RootedValue thisv(cx, args.get(0));
+
+  Rooted<ValueVector> nargs(cx, ValueVector(cx));
+  if (args.length() >= 2 && !args[1].isNullOrUndefined()) {
+    if (!args[1].isObject()) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_BAD_APPLY_ARGS, js_apply_str);
+      return false;
+    }
+
+    RootedObject argsobj(cx, &args[1].toObject());
+
+    unsigned argc = 0;
+    if (!GetLengthProperty(cx, argsobj, &argc)) {
+      return false;
+    }
+    argc = unsigned(std::min(argc, ARGS_LENGTH_MAX));
+
+    if (!nargs.growBy(argc) || !GetElements(cx, argsobj, argc, nargs.begin())) {
+      return false;
+    }
+  }
+
+  Rooted<Maybe<Completion>> completion(
+      cx, DebuggerObject::call(cx, object, thisv, nargs));
+  if (!completion.get()) {
+    return false;
+  }
+
+  return completion->buildCompletionValue(cx, object->owner(), args.rval());
+}
+
+static void EnterDebuggeeObjectRealm(JSContext* cx, Maybe<AutoRealm>& ar,
+                                     JSObject* referent) {
+  // |referent| may be a cross-compartment wrapper and CCWs normally
+  // shouldn't be used with AutoRealm, but here we use an arbitrary realm for
+  // now because we don't really have another option.
+  ar.emplace(cx, referent->maybeCCWRealm()->maybeGlobal());
+}
+
+static bool RequireGlobalObject(JSContext* cx, HandleValue dbgobj,
+                                HandleObject referent) {
+  RootedObject obj(cx, referent);
+
+  if (!obj->is<GlobalObject>()) {
+    const char* isWrapper = "";
+    const char* isWindowProxy = "";
+
+    // Help the poor programmer by pointing out wrappers around globals...
+    if (obj->is<WrapperObject>()) {
+      obj = js::UncheckedUnwrap(obj);
+      isWrapper = "a wrapper around ";
+    }
+
+    // ... and WindowProxies around Windows.
+    if (IsWindowProxy(obj)) {
+      obj = ToWindowIfWindowProxy(obj);
+      isWindowProxy = "a WindowProxy referring to ";
+    }
+
+    if (obj->is<GlobalObject>()) {
+      ReportValueError(cx, JSMSG_DEBUG_WRAPPER_IN_WAY, JSDVG_SEARCH_STACK,
+                       dbgobj, nullptr, isWrapper, isWindowProxy);
+    } else {
+      ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK, dbgobj,
+                       nullptr, "a global object");
+    }
+    return false;
+  }
+
+  return true;
+}
+
+bool DebuggerObject::CallData::asEnvironmentMethod() {
+  Debugger* dbg = object->owner();
+
+  if (!RequireGlobalObject(cx, args.thisv(), referent)) {
+    return false;
+  }
+
+  Rooted<Env*> env(cx);
+  {
+    AutoRealm ar(cx, referent);
+    env = GetDebugEnvironmentForGlobalLexicalEnvironment(cx);
+    if (!env) {
+      return false;
+    }
+  }
+
+  return dbg->wrapEnvironment(cx, env, args.rval());
+}
+
+// Lookup a binding on the referent's global scope and change it to undefined
+// if it is an uninitialized lexical, otherwise do nothing. The method's
+// JavaScript return value is true _only_ when an uninitialized lexical has been
+// altered, otherwise it is false.
+bool DebuggerObject::CallData::forceLexicalInitializationByNameMethod() {
+  if (!args.requireAtLeast(
+          cx, "Debugger.Object.prototype.forceLexicalInitializationByName",
+          1)) {
+    return false;
+  }
+
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+
+  RootedId id(cx);
+  if (!ValueToIdentifier(cx, args[0], &id)) {
+    return false;
+  }
+
+  bool result;
+  if (!DebuggerObject::forceLexicalInitializationByName(cx, object, id,
+                                                        result)) {
+    return false;
+  }
+
+  args.rval().setBoolean(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::executeInGlobalMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.prototype.executeInGlobal",
+                           1)) {
+    return false;
+  }
+
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+
+  AutoStableStringChars stableChars(cx);
+  if (!ValueToStableChars(cx, "Debugger.Object.prototype.executeInGlobal",
+                          args[0], stableChars)) {
+    return false;
+  }
+  mozilla::Range<const char16_t> chars = stableChars.twoByteRange();
+
+  EvalOptions options;
+  if (!ParseEvalOptions(cx, args.get(1), options)) {
+    return false;
+  }
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(
+      cx, comp,
+      DebuggerObject::executeInGlobal(cx, object, chars, nullptr, options));
+  return comp.get().buildCompletionValue(cx, object->owner(), args.rval());
+}
+
+bool DebuggerObject::CallData::executeInGlobalWithBindingsMethod() {
+  if (!args.requireAtLeast(
+          cx, "Debugger.Object.prototype.executeInGlobalWithBindings", 2)) {
+    return false;
+  }
+
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+
+  AutoStableStringChars stableChars(cx);
+  if (!ValueToStableChars(
+          cx, "Debugger.Object.prototype.executeInGlobalWithBindings", args[0],
+          stableChars)) {
+    return false;
+  }
+  mozilla::Range<const char16_t> chars = stableChars.twoByteRange();
+
+  RootedObject bindings(cx, RequireObject(cx, args[1]));
+  if (!bindings) {
+    return false;
+  }
+
+  EvalOptions options;
+  if (!ParseEvalOptions(cx, args.get(2), options)) {
+    return false;
+  }
+
+  Rooted<Completion> comp(cx);
+  JS_TRY_VAR_OR_RETURN_FALSE(
+      cx, comp,
+      DebuggerObject::executeInGlobal(cx, object, chars, bindings, options));
+  return comp.get().buildCompletionValue(cx, object->owner(), args.rval());
+}
+
+// Copy a narrow or wide string to a vector, appending a null terminator.
+template <typename T>
+static bool CopyStringToVector(JSContext* cx, JSString* str, Vector<T>& chars) {
+  JSLinearString* linear = str->ensureLinear(cx);
+  if (!linear) {
+    return false;
+  }
+  if (!chars.appendN(0, linear->length() + 1)) {
+    return false;
+  }
+  CopyChars(chars.begin(), *linear);
+  return true;
+}
+
+bool DebuggerObject::CallData::createSource() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.prototype.createSource", 1)) {
+    return false;
+  }
+
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+
+  RootedObject options(cx, ToObject(cx, args[0]));
+  if (!options) {
+    return false;
+  }
+
+  RootedValue v(cx);
+  if (!JS_GetProperty(cx, options, "text", &v)) {
+    return false;
+  }
+
+  RootedString text(cx, ToString<CanGC>(cx, v));
+  if (!text) {
+    return false;
+  }
+
+  if (!JS_GetProperty(cx, options, "url", &v)) {
+    return false;
+  }
+
+  RootedString url(cx, ToString<CanGC>(cx, v));
+  if (!url) {
+    return false;
+  }
+
+  if (!JS_GetProperty(cx, options, "startLine", &v)) {
+    return false;
+  }
+
+  uint32_t startLine;
+  if (!ToUint32(cx, v, &startLine)) {
+    return false;
+  }
+
+  if (!JS_GetProperty(cx, options, "sourceMapURL", &v)) {
+    return false;
+  }
+
+  RootedString sourceMapURL(cx);
+  if (!v.isUndefined()) {
+    sourceMapURL = ToString<CanGC>(cx, v);
+    if (!sourceMapURL) {
+      return false;
+    }
+  }
+
+  if (!JS_GetProperty(cx, options, "isScriptElement", &v)) {
+    return false;
+  }
+
+  bool isScriptElement = ToBoolean(v);
+
+  JS::CompileOptions compileOptions(cx);
+  compileOptions.lineno = startLine;
+
+  if (!JS::StringHasLatin1Chars(url)) {
+    JS_ReportErrorASCII(cx, "URL must be a narrow string");
+    return false;
+  }
+
+  Vector<Latin1Char> urlChars(cx);
+  if (!CopyStringToVector(cx, url, urlChars)) {
+    return false;
+  }
+  compileOptions.setFile((const char*)urlChars.begin());
+
+  Vector<char16_t> sourceMapURLChars(cx);
+  if (sourceMapURL) {
+    if (!CopyStringToVector(cx, sourceMapURL, sourceMapURLChars)) {
+      return false;
+    }
+    compileOptions.setSourceMapURL(sourceMapURLChars.begin());
+  }
+
+  if (isScriptElement) {
+    // The introduction type must be a statically allocated string.
+    compileOptions.setIntroductionType("inlineScript");
+  }
+
+  Vector<char16_t> textChars(cx);
+  if (!CopyStringToVector(cx, text, textChars)) {
+    return false;
+  }
+
+  JS::SourceText<char16_t> srcBuf;
+  if (!srcBuf.init(cx, textChars.begin(), text->length(),
+                   JS::SourceOwnership::Borrowed)) {
+    return false;
+  }
+
+  RootedScript script(cx);
+  {
+    AutoRealm ar(cx, object->referent());
+    script = JS::Compile(cx, compileOptions, srcBuf);
+    if (!script) {
+      return false;
+    }
+  }
+
+  RootedScriptSourceObject sso(cx, script->sourceObject());
+  RootedObject wrapped(cx, object->owner()->wrapSource(cx, sso));
+  if (!wrapped) {
+    return false;
+  }
+
+  args.rval().setObject(*wrapped);
+  return true;
+}
+
+bool DebuggerObject::CallData::makeDebuggeeValueMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.prototype.makeDebuggeeValue",
+                           1)) {
+    return false;
+  }
+
+  return DebuggerObject::makeDebuggeeValue(cx, object, args[0], args.rval());
+}
+
+bool DebuggerObject::CallData::makeDebuggeeNativeFunctionMethod() {
+  if (!args.requireAtLeast(
+          cx, "Debugger.Object.prototype.makeDebuggeeNativeFunction", 1)) {
+    return false;
+  }
+
+  return DebuggerObject::makeDebuggeeNativeFunction(cx, object, args[0],
+                                                    args.rval());
+}
+
+bool DebuggerObject::CallData::isSameNativeMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.prototype.isSameNative", 1)) {
+    return false;
+  }
+
+  return DebuggerObject::isSameNative(cx, object, args[0], args.rval());
+}
+
+bool DebuggerObject::CallData::unsafeDereferenceMethod() {
+  RootedObject result(cx);
+  if (!DebuggerObject::unsafeDereference(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerObject::CallData::unwrapMethod() {
+  RootedDebuggerObject result(cx);
+  if (!DebuggerObject::unwrap(cx, object, &result)) {
+    return false;
+  }
+
+  args.rval().setObjectOrNull(result);
+  return true;
+}
+
+bool DebuggerObject::CallData::setInstrumentationMethod() {
+  if (!args.requireAtLeast(cx, "Debugger.Object.prototype.setInstrumentation",
+                           2)) {
+    return false;
+  }
+
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+  RootedGlobalObject global(cx, &object->referent()->as<GlobalObject>());
+
+  RootedValue v(cx, args[0]);
+  if (!object->owner()->unwrapDebuggeeValue(cx, &v)) {
+    return false;
+  }
+  if (!v.isObject()) {
+    JS_ReportErrorASCII(cx, "Instrumentation callback must be an object");
+    return false;
+  }
+  RootedObject callback(cx, &v.toObject());
+
+  if (!args[1].isObject()) {
+    JS_ReportErrorASCII(cx, "Instrumentation kinds must be an object");
+    return false;
+  }
+  RootedObject kindsObj(cx, &args[1].toObject());
+
+  unsigned length = 0;
+  if (!GetLengthProperty(cx, kindsObj, &length)) {
+    return false;
+  }
+
+  Rooted<ValueVector> values(cx, ValueVector(cx));
+  if (!values.growBy(length) ||
+      !GetElements(cx, kindsObj, length, values.begin())) {
+    return false;
+  }
+
+  Rooted<StringVector> kinds(cx, StringVector(cx));
+  for (size_t i = 0; i < values.length(); i++) {
+    if (!values[i].isString()) {
+      JS_ReportErrorASCII(cx, "Instrumentation kind must be a string");
+      return false;
+    }
+    if (!kinds.append(values[i].toString())) {
+      return false;
+    }
+  }
+
+  {
+    AutoRealm ar(cx, global);
+    RootedObject dbgObject(cx, object->owner()->toJSObject());
+    if (!RealmInstrumentation::install(cx, global, callback, dbgObject,
+                                       kinds)) {
+      return false;
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerObject::CallData::setInstrumentationActiveMethod() {
+  if (!DebuggerObject::requireGlobal(cx, object)) {
+    return false;
+  }
+
+  if (!args.requireAtLeast(
+          cx, "Debugger.Object.prototype.setInstrumentationActive", 1)) {
+    return false;
+  }
+
+  RootedGlobalObject global(cx, &object->referent()->as<GlobalObject>());
+  bool active = ToBoolean(args[0]);
+
+  {
+    AutoRealm ar(cx, global);
+    if (!RealmInstrumentation::setActive(cx, global, object->owner(), active)) {
+      return false;
+    }
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+struct DebuggerObject::PromiseReactionRecordBuilder
+    : js::PromiseReactionRecordBuilder {
+  Debugger* dbg;
+  HandleArrayObject records;
+
+  PromiseReactionRecordBuilder(Debugger* dbg, HandleArrayObject records)
+      : dbg(dbg), records(records) {}
+
+  bool then(JSContext* cx, HandleObject resolve, HandleObject reject,
+            HandleObject result) override {
+    RootedPlainObject record(cx, NewBuiltinClassInstance<PlainObject>(cx));
+    if (!record) {
+      return false;
+    }
+
+    if (!setIfNotNull(cx, record, cx->names().resolve, resolve) ||
+        !setIfNotNull(cx, record, cx->names().reject, reject) ||
+        !setIfNotNull(cx, record, cx->names().result, result)) {
+      return false;
+    }
+
+    return push(cx, record);
+  }
+
+  bool direct(JSContext* cx, Handle<PromiseObject*> unwrappedPromise) override {
+    RootedValue v(cx, ObjectValue(*unwrappedPromise));
+    return dbg->wrapDebuggeeValue(cx, &v) && push(cx, v);
+  }
+
+  bool asyncFunction(
+      JSContext* cx,
+      Handle<AsyncFunctionGeneratorObject*> unwrappedGenerator) override {
+    return pushGenerator(cx, unwrappedGenerator);
+  }
+
+  bool asyncGenerator(
+      JSContext* cx,
+      Handle<AsyncGeneratorObject*> unwrappedGenerator) override {
+    return pushGenerator(cx, unwrappedGenerator);
+  }
+
+ private:
+  bool push(JSContext* cx, HandleObject record) {
+    RootedValue recordVal(cx, ObjectValue(*record));
+    return push(cx, recordVal);
+  }
+
+  bool push(JSContext* cx, HandleValue recordVal) {
+    return NewbornArrayPush(cx, records, recordVal);
+  }
+
+  bool pushGenerator(JSContext* cx,
+                     Handle<AbstractGeneratorObject*> unwrappedGenerator) {
+    RootedDebuggerFrame frame(cx);
+    return dbg->getFrame(cx, unwrappedGenerator, &frame) && push(cx, frame);
+  }
+
+  bool setIfNotNull(JSContext* cx, HandlePlainObject obj,
+                    Handle<PropertyName*> name, HandleObject prop) {
+    if (!prop) {
+      return true;
+    }
+
+    RootedValue v(cx, ObjectValue(*prop));
+    if (!dbg->wrapDebuggeeValue(cx, &v) ||
+        !DefineDataProperty(cx, obj, name, v)) {
+      return false;
+    }
+
+    return true;
+  }
+};
+
+bool DebuggerObject::CallData::getPromiseReactionsMethod() {
+  Debugger* dbg = object->owner();
+
+  Rooted<PromiseObject*> unwrappedPromise(cx, EnsurePromise(cx, referent));
+  if (!unwrappedPromise) {
+    return false;
+  }
+
+  RootedArrayObject holder(cx, NewDenseEmptyArray(cx));
+  if (!holder) {
+    return false;
+  }
+
+  PromiseReactionRecordBuilder builder(dbg, holder);
+  if (!unwrappedPromise->forEachReactionRecord(cx, builder)) {
+    return false;
+  }
+
+  args.rval().setObject(*builder.records);
+  return true;
+}
+
+const JSPropertySpec DebuggerObject::properties_[] = {
+    JS_DEBUG_PSG("callable", callableGetter),
+    JS_DEBUG_PSG("isBoundFunction", isBoundFunctionGetter),
+    JS_DEBUG_PSG("isArrowFunction", isArrowFunctionGetter),
+    JS_DEBUG_PSG("isGeneratorFunction", isGeneratorFunctionGetter),
+    JS_DEBUG_PSG("isAsyncFunction", isAsyncFunctionGetter),
+    JS_DEBUG_PSG("isClassConstructor", isClassConstructorGetter),
+    JS_DEBUG_PSG("proto", protoGetter),
+    JS_DEBUG_PSG("class", classGetter),
+    JS_DEBUG_PSG("name", nameGetter),
+    JS_DEBUG_PSG("displayName", displayNameGetter),
+    JS_DEBUG_PSG("parameterNames", parameterNamesGetter),
+    JS_DEBUG_PSG("script", scriptGetter),
+    JS_DEBUG_PSG("environment", environmentGetter),
+    JS_DEBUG_PSG("boundTargetFunction", boundTargetFunctionGetter),
+    JS_DEBUG_PSG("boundThis", boundThisGetter),
+    JS_DEBUG_PSG("boundArguments", boundArgumentsGetter),
+    JS_DEBUG_PSG("allocationSite", allocationSiteGetter),
+    JS_DEBUG_PSG("isError", isErrorGetter),
+    JS_DEBUG_PSG("errorMessageName", errorMessageNameGetter),
+    JS_DEBUG_PSG("errorNotes", errorNotesGetter),
+    JS_DEBUG_PSG("errorLineNumber", errorLineNumberGetter),
+    JS_DEBUG_PSG("errorColumnNumber", errorColumnNumberGetter),
+    JS_DEBUG_PSG("isProxy", isProxyGetter),
+    JS_DEBUG_PSG("proxyTarget", proxyTargetGetter),
+    JS_DEBUG_PSG("proxyHandler", proxyHandlerGetter),
+    JS_PS_END};
+
+const JSPropertySpec DebuggerObject::promiseProperties_[] = {
+    JS_DEBUG_PSG("isPromise", isPromiseGetter),
+    JS_DEBUG_PSG("promiseState", promiseStateGetter),
+    JS_DEBUG_PSG("promiseValue", promiseValueGetter),
+    JS_DEBUG_PSG("promiseReason", promiseReasonGetter),
+    JS_DEBUG_PSG("promiseLifetime", promiseLifetimeGetter),
+    JS_DEBUG_PSG("promiseTimeToResolution", promiseTimeToResolutionGetter),
+    JS_DEBUG_PSG("promiseAllocationSite", promiseAllocationSiteGetter),
+    JS_DEBUG_PSG("promiseResolutionSite", promiseResolutionSiteGetter),
+    JS_DEBUG_PSG("promiseID", promiseIDGetter),
+    JS_DEBUG_PSG("promiseDependentPromises", promiseDependentPromisesGetter),
+    JS_PS_END};
+
+const JSFunctionSpec DebuggerObject::methods_[] = {
+    JS_DEBUG_FN("isExtensible", isExtensibleMethod, 0),
+    JS_DEBUG_FN("isSealed", isSealedMethod, 0),
+    JS_DEBUG_FN("isFrozen", isFrozenMethod, 0),
+    JS_DEBUG_FN("getProperty", getPropertyMethod, 0),
+    JS_DEBUG_FN("setProperty", setPropertyMethod, 0),
+    JS_DEBUG_FN("getOwnPropertyNames", getOwnPropertyNamesMethod, 0),
+    JS_DEBUG_FN("getOwnPropertySymbols", getOwnPropertySymbolsMethod, 0),
+    JS_DEBUG_FN("getOwnPropertyDescriptor", getOwnPropertyDescriptorMethod, 1),
+    JS_DEBUG_FN("preventExtensions", preventExtensionsMethod, 0),
+    JS_DEBUG_FN("seal", sealMethod, 0),
+    JS_DEBUG_FN("freeze", freezeMethod, 0),
+    JS_DEBUG_FN("defineProperty", definePropertyMethod, 2),
+    JS_DEBUG_FN("defineProperties", definePropertiesMethod, 1),
+    JS_DEBUG_FN("deleteProperty", deletePropertyMethod, 1),
+    JS_DEBUG_FN("call", callMethod, 0),
+    JS_DEBUG_FN("apply", applyMethod, 0),
+    JS_DEBUG_FN("asEnvironment", asEnvironmentMethod, 0),
+    JS_DEBUG_FN("forceLexicalInitializationByName",
+                forceLexicalInitializationByNameMethod, 1),
+    JS_DEBUG_FN("executeInGlobal", executeInGlobalMethod, 1),
+    JS_DEBUG_FN("executeInGlobalWithBindings",
+                executeInGlobalWithBindingsMethod, 2),
+    JS_DEBUG_FN("createSource", createSource, 1),
+    JS_DEBUG_FN("makeDebuggeeValue", makeDebuggeeValueMethod, 1),
+    JS_DEBUG_FN("makeDebuggeeNativeFunction", makeDebuggeeNativeFunctionMethod,
+                1),
+    JS_DEBUG_FN("isSameNative", isSameNativeMethod, 1),
+    JS_DEBUG_FN("unsafeDereference", unsafeDereferenceMethod, 0),
+    JS_DEBUG_FN("unwrap", unwrapMethod, 0),
+    JS_DEBUG_FN("setInstrumentation", setInstrumentationMethod, 2),
+    JS_DEBUG_FN("setInstrumentationActive", setInstrumentationActiveMethod, 1),
+    JS_DEBUG_FN("getPromiseReactions", getPromiseReactionsMethod, 0),
+    JS_FS_END};
+
+/* static */
+NativeObject* DebuggerObject::initClass(JSContext* cx,
+                                        Handle<GlobalObject*> global,
+                                        HandleObject debugCtor) {
+  RootedNativeObject objectProto(
+      cx, InitClass(cx, debugCtor, nullptr, &class_, construct, 0, properties_,
+                    methods_, nullptr, nullptr));
+
+  if (!objectProto) {
+    return nullptr;
+  }
+
+  if (!DefinePropertiesAndFunctions(cx, objectProto, promiseProperties_,
+                                    nullptr)) {
+    return nullptr;
+  }
+
+  return objectProto;
+}
+
+/* static */
+DebuggerObject* DebuggerObject::create(JSContext* cx, HandleObject proto,
+                                       HandleObject referent,
+                                       HandleNativeObject debugger) {
+  DebuggerObject* obj =
+      IsInsideNursery(referent)
+          ? NewObjectWithGivenProto<DebuggerObject>(cx, proto)
+          : NewTenuredObjectWithGivenProto<DebuggerObject>(cx, proto);
+  if (!obj) {
+    return nullptr;
+  }
+
+  obj->setPrivateGCThing(referent);
+  obj->setReservedSlot(OWNER_SLOT, ObjectValue(*debugger));
+
+  return obj;
+}
+
+bool DebuggerObject::isCallable() const { return referent()->isCallable(); }
+
+bool DebuggerObject::isFunction() const { return referent()->is<JSFunction>(); }
+
+bool DebuggerObject::isDebuggeeFunction() const {
+  return referent()->is<JSFunction>() &&
+         owner()->observesGlobal(&referent()->as<JSFunction>().global());
+}
+
+bool DebuggerObject::isBoundFunction() const {
+  MOZ_ASSERT(isDebuggeeFunction());
+
+  return referent()->isBoundFunction();
+}
+
+bool DebuggerObject::isArrowFunction() const {
+  MOZ_ASSERT(isDebuggeeFunction());
+
+  return referent()->as<JSFunction>().isArrow();
+}
+
+bool DebuggerObject::isAsyncFunction() const {
+  MOZ_ASSERT(isDebuggeeFunction());
+
+  return referent()->as<JSFunction>().isAsync();
+}
+
+bool DebuggerObject::isGeneratorFunction() const {
+  MOZ_ASSERT(isDebuggeeFunction());
+
+  return referent()->as<JSFunction>().isGenerator();
+}
+
+bool DebuggerObject::isClassConstructor() const {
+  MOZ_ASSERT(isDebuggeeFunction());
+
+  return referent()->as<JSFunction>().isClassConstructor();
+}
+
+bool DebuggerObject::isGlobal() const { return referent()->is<GlobalObject>(); }
+
+bool DebuggerObject::isScriptedProxy() const {
+  return js::IsScriptedProxy(referent());
+}
+
+bool DebuggerObject::isPromise() const {
+  JSObject* referent = this->referent();
+
+  if (IsCrossCompartmentWrapper(referent)) {
+    // We only care about promises, so CheckedUnwrapStatic is OK.
+    referent = CheckedUnwrapStatic(referent);
+    if (!referent) {
+      return false;
+    }
+  }
+
+  return referent->is<PromiseObject>();
+}
+
+bool DebuggerObject::isError() const {
+  JSObject* referent = this->referent();
+
+  if (IsCrossCompartmentWrapper(referent)) {
+    // We only check for error classes, so CheckedUnwrapStatic is OK.
+    referent = CheckedUnwrapStatic(referent);
+    if (!referent) {
+      return false;
+    }
+  }
+
+  return referent->is<ErrorObject>();
+}
+
+/* static */
+bool DebuggerObject::getClassName(JSContext* cx, HandleDebuggerObject object,
+                                  MutableHandleString result) {
+  RootedObject referent(cx, object->referent());
+
+  const char* className;
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+    className = GetObjectClassName(cx, referent);
+  }
+
+  JSAtom* str = Atomize(cx, className, strlen(className));
+  if (!str) {
+    return false;
+  }
+
+  result.set(str);
+  return true;
+}
+
+JSAtom* DebuggerObject::name(JSContext* cx) const {
+  MOZ_ASSERT(isFunction());
+
+  JSAtom* atom = referent()->as<JSFunction>().explicitName();
+  if (atom) {
+    cx->markAtom(atom);
+  }
+  return atom;
+}
+
+JSAtom* DebuggerObject::displayName(JSContext* cx) const {
+  MOZ_ASSERT(isFunction());
+
+  JSAtom* atom = referent()->as<JSFunction>().displayAtom();
+  if (atom) {
+    cx->markAtom(atom);
+  }
+  return atom;
+}
+
+JS::PromiseState DebuggerObject::promiseState() const {
+  return promise()->state();
+}
+
+double DebuggerObject::promiseLifetime() const { return promise()->lifetime(); }
+
+double DebuggerObject::promiseTimeToResolution() const {
+  MOZ_ASSERT(promiseState() != JS::PromiseState::Pending);
+
+  return promise()->timeToResolution();
+}
+
+/* static */
+bool DebuggerObject::getBoundTargetFunction(
+    JSContext* cx, HandleDebuggerObject object,
+    MutableHandleDebuggerObject result) {
+  MOZ_ASSERT(object->isBoundFunction());
+
+  RootedFunction referent(cx, &object->referent()->as<JSFunction>());
+  Debugger* dbg = object->owner();
+
+  RootedObject target(cx, referent->getBoundFunctionTarget());
+  return dbg->wrapDebuggeeObject(cx, target, result);
+}
+
+/* static */
+bool DebuggerObject::getBoundThis(JSContext* cx, HandleDebuggerObject object,
+                                  MutableHandleValue result) {
+  MOZ_ASSERT(object->isBoundFunction());
+
+  RootedFunction referent(cx, &object->referent()->as<JSFunction>());
+  Debugger* dbg = object->owner();
+
+  result.set(referent->getBoundFunctionThis());
+  return dbg->wrapDebuggeeValue(cx, result);
+}
+
+/* static */
+bool DebuggerObject::getBoundArguments(JSContext* cx,
+                                       HandleDebuggerObject object,
+                                       MutableHandle<ValueVector> result) {
+  MOZ_ASSERT(object->isBoundFunction());
+
+  RootedFunction referent(cx, &object->referent()->as<JSFunction>());
+  Debugger* dbg = object->owner();
+
+  size_t length = referent->getBoundFunctionArgumentCount();
+  if (!result.resize(length)) {
+    return false;
+  }
+  for (size_t i = 0; i < length; i++) {
+    result[i].set(referent->getBoundFunctionArgument(i));
+    if (!dbg->wrapDebuggeeValue(cx, result[i])) {
+      return false;
+    }
+  }
+  return true;
+}
+
+/* static */
+SavedFrame* Debugger::getObjectAllocationSite(JSObject& obj) {
+  JSObject* metadata = GetAllocationMetadata(&obj);
+  if (!metadata) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(!metadata->is<WrapperObject>());
+  return metadata->is<SavedFrame>() ? &metadata->as<SavedFrame>() : nullptr;
+}
+
+/* static */
+bool DebuggerObject::getAllocationSite(JSContext* cx,
+                                       HandleDebuggerObject object,
+                                       MutableHandleObject result) {
+  RootedObject referent(cx, object->referent());
+
+  RootedObject allocSite(cx, Debugger::getObjectAllocationSite(*referent));
+  if (!cx->compartment()->wrap(cx, &allocSite)) {
+    return false;
+  }
+
+  result.set(allocSite);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getErrorReport(JSContext* cx, HandleObject maybeError,
+                                    JSErrorReport*& report) {
+  JSObject* obj = maybeError;
+  if (IsCrossCompartmentWrapper(obj)) {
+    /* We only care about Error objects, so CheckedUnwrapStatic is OK. */
+    obj = CheckedUnwrapStatic(obj);
+  }
+
+  if (!obj) {
+    ReportAccessDenied(cx);
+    return false;
+  }
+
+  if (!obj->is<ErrorObject>()) {
+    report = nullptr;
+    return true;
+  }
+
+  report = obj->as<ErrorObject>().getErrorReport();
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getErrorMessageName(JSContext* cx,
+                                         HandleDebuggerObject object,
+                                         MutableHandleString result) {
+  RootedObject referent(cx, object->referent());
+  JSErrorReport* report;
+  if (!getErrorReport(cx, referent, report)) {
+    return false;
+  }
+
+  if (!report || !report->errorMessageName) {
+    result.set(nullptr);
+    return true;
+  }
+
+  RootedString str(cx, JS_NewStringCopyZ(cx, report->errorMessageName));
+  if (!str) {
+    return false;
+  }
+  result.set(str);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getErrorNotes(JSContext* cx, HandleDebuggerObject object,
+                                   MutableHandleValue result) {
+  RootedObject referent(cx, object->referent());
+  JSErrorReport* report;
+  if (!getErrorReport(cx, referent, report)) {
+    return false;
+  }
+
+  if (!report) {
+    result.setUndefined();
+    return true;
+  }
+
+  RootedObject errorNotesArray(cx, CreateErrorNotesArray(cx, report));
+  if (!errorNotesArray) {
+    return false;
+  }
+
+  if (!cx->compartment()->wrap(cx, &errorNotesArray)) {
+    return false;
+  }
+  result.setObject(*errorNotesArray);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getErrorLineNumber(JSContext* cx,
+                                        HandleDebuggerObject object,
+                                        MutableHandleValue result) {
+  RootedObject referent(cx, object->referent());
+  JSErrorReport* report;
+  if (!getErrorReport(cx, referent, report)) {
+    return false;
+  }
+
+  if (!report) {
+    result.setUndefined();
+    return true;
+  }
+
+  result.setNumber(report->lineno);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getErrorColumnNumber(JSContext* cx,
+                                          HandleDebuggerObject object,
+                                          MutableHandleValue result) {
+  RootedObject referent(cx, object->referent());
+  JSErrorReport* report;
+  if (!getErrorReport(cx, referent, report)) {
+    return false;
+  }
+
+  if (!report) {
+    result.setUndefined();
+    return true;
+  }
+
+  result.setNumber(report->column);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getPromiseValue(JSContext* cx, HandleDebuggerObject object,
+                                     MutableHandleValue result) {
+  MOZ_ASSERT(object->promiseState() == JS::PromiseState::Fulfilled);
+
+  result.set(object->promise()->value());
+  return object->owner()->wrapDebuggeeValue(cx, result);
+}
+
+/* static */
+bool DebuggerObject::getPromiseReason(JSContext* cx,
+                                      HandleDebuggerObject object,
+                                      MutableHandleValue result) {
+  MOZ_ASSERT(object->promiseState() == JS::PromiseState::Rejected);
+
+  result.set(object->promise()->reason());
+  return object->owner()->wrapDebuggeeValue(cx, result);
+}
+
+/* static */
+bool DebuggerObject::isExtensible(JSContext* cx, HandleDebuggerObject object,
+                                  bool& result) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return IsExtensible(cx, referent, &result);
+}
+
+/* static */
+bool DebuggerObject::isSealed(JSContext* cx, HandleDebuggerObject object,
+                              bool& result) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return TestIntegrityLevel(cx, referent, IntegrityLevel::Sealed, &result);
+}
+
+/* static */
+bool DebuggerObject::isFrozen(JSContext* cx, HandleDebuggerObject object,
+                              bool& result) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return TestIntegrityLevel(cx, referent, IntegrityLevel::Frozen, &result);
+}
+
+/* static */
+bool DebuggerObject::getPrototypeOf(JSContext* cx, HandleDebuggerObject object,
+                                    MutableHandleDebuggerObject result) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  RootedObject proto(cx);
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+    if (!GetPrototype(cx, referent, &proto)) {
+      return false;
+    }
+  }
+
+  return dbg->wrapNullableDebuggeeObject(cx, proto, result);
+}
+
+/* static */
+bool DebuggerObject::getOwnPropertyNames(JSContext* cx,
+                                         HandleDebuggerObject object,
+                                         MutableHandle<IdVector> result) {
+  RootedObject referent(cx, object->referent());
+
+  RootedIdVector ids(cx);
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+
+    ErrorCopier ec(ar);
+    if (!GetPropertyKeys(cx, referent, JSITER_OWNONLY | JSITER_HIDDEN, &ids)) {
+      return false;
+    }
+  }
+
+  for (size_t i = 0; i < ids.length(); i++) {
+    cx->markId(ids[i]);
+  }
+
+  return result.append(ids.begin(), ids.end());
+}
+
+/* static */
+bool DebuggerObject::getOwnPropertySymbols(JSContext* cx,
+                                           HandleDebuggerObject object,
+                                           MutableHandle<IdVector> result) {
+  RootedObject referent(cx, object->referent());
+
+  RootedIdVector ids(cx);
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+
+    ErrorCopier ec(ar);
+    if (!GetPropertyKeys(cx, referent,
+                         JSITER_OWNONLY | JSITER_HIDDEN | JSITER_SYMBOLS |
+                             JSITER_SYMBOLSONLY,
+                         &ids)) {
+      return false;
+    }
+  }
+
+  for (size_t i = 0; i < ids.length(); i++) {
+    cx->markId(ids[i]);
+  }
+
+  return result.append(ids.begin(), ids.end());
+}
+
+/* static */
+bool DebuggerObject::getOwnPropertyDescriptor(
+    JSContext* cx, HandleDebuggerObject object, HandleId id,
+    MutableHandle<PropertyDescriptor> desc) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  // Bug: This can cause the debuggee to run!
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+
+    cx->markId(id);
+
+    ErrorCopier ec(ar);
+    if (!GetOwnPropertyDescriptor(cx, referent, id, desc)) {
+      return false;
+    }
+  }
+
+  if (desc.object()) {
+    // Rewrap the debuggee values in desc for the debugger.
+    if (!dbg->wrapDebuggeeValue(cx, desc.value())) {
+      return false;
+    }
+
+    if (desc.hasGetterObject()) {
+      RootedValue get(cx, ObjectOrNullValue(desc.getterObject()));
+      if (!dbg->wrapDebuggeeValue(cx, &get)) {
+        return false;
+      }
+      desc.setGetterObject(get.toObjectOrNull());
+    }
+    if (desc.hasSetterObject()) {
+      RootedValue set(cx, ObjectOrNullValue(desc.setterObject()));
+      if (!dbg->wrapDebuggeeValue(cx, &set)) {
+        return false;
+      }
+      desc.setSetterObject(set.toObjectOrNull());
+    }
+
+    // Avoid tripping same-compartment assertions in
+    // JS::FromPropertyDescriptor().
+    desc.object().set(object);
+  }
+
+  return true;
+}
+
+/* static */
+bool DebuggerObject::preventExtensions(JSContext* cx,
+                                       HandleDebuggerObject object) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return PreventExtensions(cx, referent);
+}
+
+/* static */
+bool DebuggerObject::seal(JSContext* cx, HandleDebuggerObject object) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return SetIntegrityLevel(cx, referent, IntegrityLevel::Sealed);
+}
+
+/* static */
+bool DebuggerObject::freeze(JSContext* cx, HandleDebuggerObject object) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  ErrorCopier ec(ar);
+  return SetIntegrityLevel(cx, referent, IntegrityLevel::Frozen);
+}
+
+/* static */
+bool DebuggerObject::defineProperty(JSContext* cx, HandleDebuggerObject object,
+                                    HandleId id,
+                                    Handle<PropertyDescriptor> desc_) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  Rooted<PropertyDescriptor> desc(cx, desc_);
+  if (!dbg->unwrapPropertyDescriptor(cx, referent, &desc)) {
+    return false;
+  }
+  JS_TRY_OR_RETURN_FALSE(cx, CheckPropertyDescriptorAccessors(cx, desc));
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  if (!cx->compartment()->wrap(cx, &desc)) {
+    return false;
+  }
+  cx->markId(id);
+
+  ErrorCopier ec(ar);
+  return DefineProperty(cx, referent, id, desc);
+}
+
+/* static */
+bool DebuggerObject::defineProperties(JSContext* cx,
+                                      HandleDebuggerObject object,
+                                      Handle<IdVector> ids,
+                                      Handle<PropertyDescriptorVector> descs_) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  Rooted<PropertyDescriptorVector> descs(cx, PropertyDescriptorVector(cx));
+  if (!descs.append(descs_.begin(), descs_.end())) {
+    return false;
+  }
+  for (size_t i = 0; i < descs.length(); i++) {
+    if (!dbg->unwrapPropertyDescriptor(cx, referent, descs[i])) {
+      return false;
+    }
+    JS_TRY_OR_RETURN_FALSE(cx, CheckPropertyDescriptorAccessors(cx, descs[i]));
+  }
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  for (size_t i = 0; i < descs.length(); i++) {
+    if (!cx->compartment()->wrap(cx, descs[i])) {
+      return false;
+    }
+    cx->markId(ids[i]);
+  }
+
+  ErrorCopier ec(ar);
+  for (size_t i = 0; i < descs.length(); i++) {
+    if (!DefineProperty(cx, referent, ids[i], descs[i])) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+/* static */
+bool DebuggerObject::deleteProperty(JSContext* cx, HandleDebuggerObject object,
+                                    HandleId id, ObjectOpResult& result) {
+  RootedObject referent(cx, object->referent());
+
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  cx->markId(id);
+
+  ErrorCopier ec(ar);
+  return DeleteProperty(cx, referent, id, result);
+}
+
+/* static */
+Result<Completion> DebuggerObject::getProperty(JSContext* cx,
+                                               HandleDebuggerObject object,
+                                               HandleId id,
+                                               HandleValue receiver_) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  // Unwrap Debugger.Objects. This happens in the debugger's compartment since
+  // that is where any exceptions must be reported.
+  RootedValue receiver(cx, receiver_);
+  if (!dbg->unwrapDebuggeeValue(cx, &receiver)) {
+    return cx->alreadyReportedError();
+  }
+
+  // Enter the debuggee compartment and rewrap all input value for that
+  // compartment. (Rewrapping always takes place in the destination
+  // compartment.)
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+  if (!cx->compartment()->wrap(cx, &referent) ||
+      !cx->compartment()->wrap(cx, &receiver)) {
+    return cx->alreadyReportedError();
+  }
+  cx->markId(id);
+
+  LeaveDebuggeeNoExecute nnx(cx);
+
+  RootedValue result(cx);
+  bool ok = GetProperty(cx, referent, receiver, id, &result);
+  return Completion::fromJSResult(cx, ok, result);
+}
+
+/* static */
+Result<Completion> DebuggerObject::setProperty(JSContext* cx,
+                                               HandleDebuggerObject object,
+                                               HandleId id, HandleValue value_,
+                                               HandleValue receiver_) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  // Unwrap Debugger.Objects. This happens in the debugger's compartment since
+  // that is where any exceptions must be reported.
+  RootedValue value(cx, value_);
+  RootedValue receiver(cx, receiver_);
+  if (!dbg->unwrapDebuggeeValue(cx, &value) ||
+      !dbg->unwrapDebuggeeValue(cx, &receiver)) {
+    return cx->alreadyReportedError();
+  }
+
+  // Enter the debuggee compartment and rewrap all input value for that
+  // compartment. (Rewrapping always takes place in the destination
+  // compartment.)
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+  if (!cx->compartment()->wrap(cx, &referent) ||
+      !cx->compartment()->wrap(cx, &value) ||
+      !cx->compartment()->wrap(cx, &receiver)) {
+    return cx->alreadyReportedError();
+  }
+  cx->markId(id);
+
+  LeaveDebuggeeNoExecute nnx(cx);
+
+  ObjectOpResult opResult;
+  bool ok = SetProperty(cx, referent, id, value, receiver, opResult);
+
+  return Completion::fromJSResult(cx, ok, BooleanValue(ok && opResult.ok()));
+}
+
+/* static */
+Maybe<Completion> DebuggerObject::call(JSContext* cx,
+                                       HandleDebuggerObject object,
+                                       HandleValue thisv_,
+                                       Handle<ValueVector> args) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  if (!referent->isCallable()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Object",
+                              "call", referent->getClass()->name);
+    return Nothing();
+  }
+
+  RootedValue calleev(cx, ObjectValue(*referent));
+
+  // Unwrap Debugger.Objects. This happens in the debugger's compartment since
+  // that is where any exceptions must be reported.
+  RootedValue thisv(cx, thisv_);
+  if (!dbg->unwrapDebuggeeValue(cx, &thisv)) {
+    return Nothing();
+  }
+  Rooted<ValueVector> args2(cx, ValueVector(cx));
+  if (!args2.append(args.begin(), args.end())) {
+    return Nothing();
+  }
+  for (size_t i = 0; i < args2.length(); ++i) {
+    if (!dbg->unwrapDebuggeeValue(cx, args2[i])) {
+      return Nothing();
+    }
+  }
+
+  // Enter the debuggee compartment and rewrap all input value for that
+  // compartment. (Rewrapping always takes place in the destination
+  // compartment.)
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+  if (!cx->compartment()->wrap(cx, &calleev) ||
+      !cx->compartment()->wrap(cx, &thisv)) {
+    return Nothing();
+  }
+  for (size_t i = 0; i < args2.length(); ++i) {
+    if (!cx->compartment()->wrap(cx, args2[i])) {
+      return Nothing();
+    }
+  }
+
+  // Call the function.
+  LeaveDebuggeeNoExecute nnx(cx);
+
+  RootedValue result(cx);
+  bool ok;
+  {
+    InvokeArgs invokeArgs(cx);
+
+    ok = invokeArgs.init(cx, args2.length());
+    if (ok) {
+      for (size_t i = 0; i < args2.length(); ++i) {
+        invokeArgs[i].set(args2[i]);
+      }
+
+      ok = js::Call(cx, calleev, thisv, invokeArgs, &result);
+    }
+  }
+
+  Rooted<Completion> completion(cx, Completion::fromJSResult(cx, ok, result));
+  ar.reset();
+  return Some(std::move(completion.get()));
+}
+
+/* static */
+bool DebuggerObject::forceLexicalInitializationByName(
+    JSContext* cx, HandleDebuggerObject object, HandleId id, bool& result) {
+  if (!JSID_IS_STRING(id)) {
+    JS_ReportErrorNumberASCII(
+        cx, GetErrorMessage, nullptr, JSMSG_NOT_EXPECTED_TYPE,
+        "Debugger.Object.prototype.forceLexicalInitializationByName", "string",
+        InformalValueTypeName(IdToValue(id)));
+    return false;
+  }
+
+  MOZ_ASSERT(object->isGlobal());
+
+  Rooted<GlobalObject*> referent(cx, &object->referent()->as<GlobalObject>());
+
+  // Shape::search can end up allocating a new BaseShape in Shape::cachify so
+  // we need to be in the right compartment here.
+  Maybe<AutoRealm> ar;
+  EnterDebuggeeObjectRealm(cx, ar, referent);
+
+  RootedObject globalLexical(cx, &referent->lexicalEnvironment());
+  RootedObject pobj(cx);
+  Rooted<PropertyResult> prop(cx);
+  if (!LookupProperty(cx, globalLexical, id, &pobj, &prop)) {
+    return false;
+  }
+
+  result = false;
+  if (prop) {
+    MOZ_ASSERT(prop.isNativeProperty());
+    Shape* shape = prop.shape();
+    Value v = globalLexical->as<NativeObject>().getSlot(shape->slot());
+    if (shape->isDataProperty() && v.isMagic() &&
+        v.whyMagic() == JS_UNINITIALIZED_LEXICAL) {
+      globalLexical->as<NativeObject>().setSlot(shape->slot(),
+                                                UndefinedValue());
+      result = true;
+    }
+  }
+
+  return true;
+}
+
+/* static */
+Result<Completion> DebuggerObject::executeInGlobal(
+    JSContext* cx, HandleDebuggerObject object,
+    mozilla::Range<const char16_t> chars, HandleObject bindings,
+    const EvalOptions& options) {
+  MOZ_ASSERT(object->isGlobal());
+
+  Rooted<GlobalObject*> referent(cx, &object->referent()->as<GlobalObject>());
+  Debugger* dbg = object->owner();
+
+  RootedObject globalLexical(cx, &referent->lexicalEnvironment());
+  return DebuggerGenericEval(cx, chars, bindings, options, dbg, globalLexical,
+                             nullptr);
+}
+
+/* static */
+bool DebuggerObject::makeDebuggeeValue(JSContext* cx,
+                                       HandleDebuggerObject object,
+                                       HandleValue value_,
+                                       MutableHandleValue result) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  RootedValue value(cx, value_);
+
+  // Non-objects are already debuggee values.
+  if (value.isObject()) {
+    // Enter this Debugger.Object's referent's compartment, and wrap the
+    // argument as appropriate for references from there.
+    {
+      Maybe<AutoRealm> ar;
+      EnterDebuggeeObjectRealm(cx, ar, referent);
+      if (!cx->compartment()->wrap(cx, &value)) {
+        return false;
+      }
+    }
+
+    // Back in the debugger's compartment, produce a new Debugger.Object
+    // instance referring to the wrapped argument.
+    if (!dbg->wrapDebuggeeValue(cx, &value)) {
+      return false;
+    }
+  }
+
+  result.set(value);
+  return true;
+}
+
+static JSFunction* EnsureNativeFunction(const Value& value,
+                                        bool allowExtended = true) {
+  if (!value.isObject() || !value.toObject().is<JSFunction>()) {
+    return nullptr;
+  }
+
+  JSFunction* fun = &value.toObject().as<JSFunction>();
+  if (!fun->isNative() || (fun->isExtended() && !allowExtended)) {
+    return nullptr;
+  }
+
+  return fun;
+}
+
+/* static */
+bool DebuggerObject::makeDebuggeeNativeFunction(JSContext* cx,
+                                                HandleDebuggerObject object,
+                                                HandleValue value,
+                                                MutableHandleValue result) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  // The logic below doesn't work with extended functions, so do not allow them.
+  RootedFunction fun(cx, EnsureNativeFunction(value,
+                                              /* allowExtended */ false));
+  if (!fun) {
+    JS_ReportErrorASCII(cx, "Need native function");
+    return false;
+  }
+
+  RootedValue newValue(cx);
+  {
+    Maybe<AutoRealm> ar;
+    EnterDebuggeeObjectRealm(cx, ar, referent);
+
+    unsigned nargs = fun->nargs();
+    RootedAtom name(cx, fun->displayAtom());
+    if (name) {
+      cx->markAtom(name);
+    }
+    JSFunction* newFun = NewNativeFunction(cx, fun->native(), nargs, name);
+    if (!newFun) {
+      return false;
+    }
+
+    newValue.setObject(*newFun);
+  }
+
+  // Back in the debugger's compartment, produce a new Debugger.Object
+  // instance referring to the wrapped argument.
+  if (!dbg->wrapDebuggeeValue(cx, &newValue)) {
+    return false;
+  }
+
+  result.set(newValue);
+  return true;
+}
+
+static JSAtom* MaybeGetSelfHostedFunctionName(const Value& v) {
+  if (!v.isObject() || !v.toObject().is<JSFunction>()) {
+    return nullptr;
+  }
+
+  JSFunction* fun = &v.toObject().as<JSFunction>();
+  if (!fun->isSelfHostedBuiltin()) {
+    return nullptr;
+  }
+
+  return GetClonedSelfHostedFunctionName(fun);
+}
+
+/* static */
+bool DebuggerObject::isSameNative(JSContext* cx, HandleDebuggerObject object,
+                                  HandleValue value,
+                                  MutableHandleValue result) {
+  RootedValue referentValue(cx, ObjectValue(*object->referent()));
+
+  RootedValue nonCCWValue(
+      cx, value.isObject() ? ObjectValue(*UncheckedUnwrap(&value.toObject()))
+                           : value);
+
+  RootedFunction fun(cx, EnsureNativeFunction(nonCCWValue));
+  if (!fun) {
+    RootedAtom selfHostedName(cx, MaybeGetSelfHostedFunctionName(nonCCWValue));
+    if (!selfHostedName) {
+      JS_ReportErrorASCII(cx, "Need native function");
+      return false;
+    }
+
+    result.setBoolean(selfHostedName ==
+                      MaybeGetSelfHostedFunctionName(referentValue));
+    return true;
+  }
+
+  RootedFunction referentFun(cx, EnsureNativeFunction(referentValue));
+  result.setBoolean(referentFun && referentFun->native() == fun->native());
+  return true;
+}
+
+/* static */
+bool DebuggerObject::unsafeDereference(JSContext* cx,
+                                       HandleDebuggerObject object,
+                                       MutableHandleObject result) {
+  RootedObject referent(cx, object->referent());
+
+  if (!cx->compartment()->wrap(cx, &referent)) {
+    return false;
+  }
+
+  // Wrapping should return the WindowProxy.
+  MOZ_ASSERT(!IsWindow(referent));
+
+  result.set(referent);
+  return true;
+}
+
+/* static */
+bool DebuggerObject::unwrap(JSContext* cx, HandleDebuggerObject object,
+                            MutableHandleDebuggerObject result) {
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+
+  RootedObject unwrapped(cx, UnwrapOneCheckedStatic(referent));
+
+  // Don't allow unwrapping to create a D.O whose referent is in an
+  // invisible-to-Debugger compartment. (If our referent is a *wrapper* to such,
+  // and the wrapper is in a visible compartment, that's fine.)
+  if (unwrapped && unwrapped->compartment()->invisibleToDebugger()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_INVISIBLE_COMPARTMENT);
+    return false;
+  }
+
+  return dbg->wrapNullableDebuggeeObject(cx, unwrapped, result);
+}
+
+/* static */
+bool DebuggerObject::requireGlobal(JSContext* cx, HandleDebuggerObject object) {
+  if (!object->isGlobal()) {
+    RootedObject referent(cx, object->referent());
+
+    const char* isWrapper = "";
+    const char* isWindowProxy = "";
+
+    // Help the poor programmer by pointing out wrappers around globals...
+    if (referent->is<WrapperObject>()) {
+      referent = js::UncheckedUnwrap(referent);
+      isWrapper = "a wrapper around ";
+    }
+
+    // ... and WindowProxies around Windows.
+    if (IsWindowProxy(referent)) {
+      referent = ToWindowIfWindowProxy(referent);
+      isWindowProxy = "a WindowProxy referring to ";
+    }
+
+    RootedValue dbgobj(cx, ObjectValue(*object));
+    if (referent->is<GlobalObject>()) {
+      ReportValueError(cx, JSMSG_DEBUG_WRAPPER_IN_WAY, JSDVG_SEARCH_STACK,
+                       dbgobj, nullptr, isWrapper, isWindowProxy);
+    } else {
+      ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK, dbgobj,
+                       nullptr, "a global object");
+    }
+    return false;
+  }
+
+  return true;
+}
+
+/* static */
+bool DebuggerObject::requirePromise(JSContext* cx,
+                                    HandleDebuggerObject object) {
+  RootedObject referent(cx, object->referent());
+
+  if (IsCrossCompartmentWrapper(referent)) {
+    /* We only care about promises, so CheckedUnwrapStatic is OK. */
+    referent = CheckedUnwrapStatic(referent);
+    if (!referent) {
+      ReportAccessDenied(cx);
+      return false;
+    }
+  }
+
+  if (!referent->is<PromiseObject>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_NOT_EXPECTED_TYPE, "Debugger", "Promise",
+                              object->getClass()->name);
+    return false;
+  }
+
+  return true;
+}
+
+/* static */
+bool DebuggerObject::getScriptedProxyTarget(
+    JSContext* cx, HandleDebuggerObject object,
+    MutableHandleDebuggerObject result) {
+  MOZ_ASSERT(object->isScriptedProxy());
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+  RootedObject unwrapped(cx, js::GetProxyTargetObject(referent));
+
+  return dbg->wrapNullableDebuggeeObject(cx, unwrapped, result);
+}
+
+/* static */
+bool DebuggerObject::getScriptedProxyHandler(
+    JSContext* cx, HandleDebuggerObject object,
+    MutableHandleDebuggerObject result) {
+  MOZ_ASSERT(object->isScriptedProxy());
+  RootedObject referent(cx, object->referent());
+  Debugger* dbg = object->owner();
+  RootedObject unwrapped(cx, ScriptedProxyHandler::handlerObject(referent));
+  return dbg->wrapNullableDebuggeeObject(cx, unwrapped, result);
+}
diff --git a/js/src/debugger/Object.h b/js/src/debugger/Object.h
new file mode 100644
index 0000000000..6ed1cc69b8
--- /dev/null
+++ b/js/src/debugger/Object.h
@@ -0,0 +1,212 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Object_h
+#define debugger_Object_h
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+#include "mozilla/Attributes.h"  // for MOZ_MUST_USE
+#include "mozilla/Maybe.h"       // for Maybe
+#include "mozilla/Range.h"       // for Range
+#include "mozilla/Result.h"      // for Result
+
+#include "jsapi.h"             // for JSContext
+#include "jstypes.h"           // for JS_PUBLIC_API
+#include "NamespaceImports.h"  // for Value, MutableHandleValue, HandleId
+
+#include "gc/Rooting.h"       // for HandleDebuggerObject
+#include "js/Promise.h"       // for PromiseState
+#include "js/Proxy.h"         // for PropertyDescriptor
+#include "vm/JSObject.h"      // for JSObject (ptr only)
+#include "vm/NativeObject.h"  // for NativeObject
+
+class JS_PUBLIC_API JSAtom;
+
+namespace js {
+
+class Completion;
+class Debugger;
+class EvalOptions;
+class GlobalObject;
+class PromiseObject;
+
+class DebuggerObject : public NativeObject {
+ public:
+  static const JSClass class_;
+
+  static NativeObject* initClass(JSContext* cx, Handle<GlobalObject*> global,
+                                 HandleObject debugCtor);
+  static DebuggerObject* create(JSContext* cx, HandleObject proto,
+                                HandleObject referent,
+                                HandleNativeObject debugger);
+
+  void trace(JSTracer* trc);
+
+  // Properties
+  static MOZ_MUST_USE bool getClassName(JSContext* cx,
+                                        HandleDebuggerObject object,
+                                        MutableHandleString result);
+  static MOZ_MUST_USE bool getBoundTargetFunction(
+      JSContext* cx, HandleDebuggerObject object,
+      MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getBoundThis(JSContext* cx,
+                                        HandleDebuggerObject object,
+                                        MutableHandleValue result);
+  static MOZ_MUST_USE bool getBoundArguments(JSContext* cx,
+                                             HandleDebuggerObject object,
+                                             MutableHandle<ValueVector> result);
+  static MOZ_MUST_USE bool getAllocationSite(JSContext* cx,
+                                             HandleDebuggerObject object,
+                                             MutableHandleObject result);
+  static MOZ_MUST_USE bool getErrorMessageName(JSContext* cx,
+                                               HandleDebuggerObject object,
+                                               MutableHandleString result);
+  static MOZ_MUST_USE bool getErrorNotes(JSContext* cx,
+                                         HandleDebuggerObject object,
+                                         MutableHandleValue result);
+  static MOZ_MUST_USE bool getErrorLineNumber(JSContext* cx,
+                                              HandleDebuggerObject object,
+                                              MutableHandleValue result);
+  static MOZ_MUST_USE bool getErrorColumnNumber(JSContext* cx,
+                                                HandleDebuggerObject object,
+                                                MutableHandleValue result);
+  static MOZ_MUST_USE bool getScriptedProxyTarget(
+      JSContext* cx, HandleDebuggerObject object,
+      MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getScriptedProxyHandler(
+      JSContext* cx, HandleDebuggerObject object,
+      MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getPromiseValue(JSContext* cx,
+                                           HandleDebuggerObject object,
+                                           MutableHandleValue result);
+  static MOZ_MUST_USE bool getPromiseReason(JSContext* cx,
+                                            HandleDebuggerObject object,
+                                            MutableHandleValue result);
+
+  // Methods
+  static MOZ_MUST_USE bool isExtensible(JSContext* cx,
+                                        HandleDebuggerObject object,
+                                        bool& result);
+  static MOZ_MUST_USE bool isSealed(JSContext* cx, HandleDebuggerObject object,
+                                    bool& result);
+  static MOZ_MUST_USE bool isFrozen(JSContext* cx, HandleDebuggerObject object,
+                                    bool& result);
+  static MOZ_MUST_USE JS::Result<Completion> getProperty(
+      JSContext* cx, HandleDebuggerObject object, HandleId id,
+      HandleValue receiver);
+  static MOZ_MUST_USE JS::Result<Completion> setProperty(
+      JSContext* cx, HandleDebuggerObject object, HandleId id,
+      HandleValue value, HandleValue receiver);
+  static MOZ_MUST_USE bool getPrototypeOf(JSContext* cx,
+                                          HandleDebuggerObject object,
+                                          MutableHandleDebuggerObject result);
+  static MOZ_MUST_USE bool getOwnPropertyNames(JSContext* cx,
+                                               HandleDebuggerObject object,
+                                               MutableHandle<IdVector> result);
+  static MOZ_MUST_USE bool getOwnPropertySymbols(
+      JSContext* cx, HandleDebuggerObject object,
+      MutableHandle<IdVector> result);
+  static MOZ_MUST_USE bool getOwnPropertyDescriptor(
+      JSContext* cx, HandleDebuggerObject object, HandleId id,
+      MutableHandle<PropertyDescriptor> desc);
+  static MOZ_MUST_USE bool preventExtensions(JSContext* cx,
+                                             HandleDebuggerObject object);
+  static MOZ_MUST_USE bool seal(JSContext* cx, HandleDebuggerObject object);
+  static MOZ_MUST_USE bool freeze(JSContext* cx, HandleDebuggerObject object);
+  static MOZ_MUST_USE bool defineProperty(JSContext* cx,
+                                          HandleDebuggerObject object,
+                                          HandleId id,
+                                          Handle<PropertyDescriptor> desc);
+  static MOZ_MUST_USE bool defineProperties(
+      JSContext* cx, HandleDebuggerObject object, Handle<IdVector> ids,
+      Handle<PropertyDescriptorVector> descs);
+  static MOZ_MUST_USE bool deleteProperty(JSContext* cx,
+                                          HandleDebuggerObject object,
+                                          HandleId id, ObjectOpResult& result);
+  static MOZ_MUST_USE mozilla::Maybe<Completion> call(
+      JSContext* cx, HandleDebuggerObject object, HandleValue thisv,
+      Handle<ValueVector> args);
+  static MOZ_MUST_USE bool forceLexicalInitializationByName(
+      JSContext* cx, HandleDebuggerObject object, HandleId id, bool& result);
+  static MOZ_MUST_USE JS::Result<Completion> executeInGlobal(
+      JSContext* cx, HandleDebuggerObject object,
+      mozilla::Range<const char16_t> chars, HandleObject bindings,
+      const EvalOptions& options);
+  static MOZ_MUST_USE bool makeDebuggeeValue(JSContext* cx,
+                                             HandleDebuggerObject object,
+                                             HandleValue value,
+                                             MutableHandleValue result);
+  static MOZ_MUST_USE bool makeDebuggeeNativeFunction(
+      JSContext* cx, HandleDebuggerObject object, HandleValue value,
+      MutableHandleValue result);
+  static MOZ_MUST_USE bool isSameNative(JSContext* cx,
+                                        HandleDebuggerObject object,
+                                        HandleValue value,
+                                        MutableHandleValue result);
+  static MOZ_MUST_USE bool unsafeDereference(JSContext* cx,
+                                             HandleDebuggerObject object,
+                                             MutableHandleObject result);
+  static MOZ_MUST_USE bool unwrap(JSContext* cx, HandleDebuggerObject object,
+                                  MutableHandleDebuggerObject result);
+
+  // Infallible properties
+  bool isCallable() const;
+  bool isFunction() const;
+  bool isDebuggeeFunction() const;
+  bool isBoundFunction() const;
+  bool isArrowFunction() const;
+  bool isAsyncFunction() const;
+  bool isGeneratorFunction() const;
+  bool isClassConstructor() const;
+  bool isGlobal() const;
+  bool isScriptedProxy() const;
+  bool isPromise() const;
+  bool isError() const;
+  JSAtom* name(JSContext* cx) const;
+  JSAtom* displayName(JSContext* cx) const;
+  JS::PromiseState promiseState() const;
+  double promiseLifetime() const;
+  double promiseTimeToResolution() const;
+
+  bool isInstance() const;
+  Debugger* owner() const;
+
+  JSObject* referent() const {
+    JSObject* obj = (JSObject*)getPrivate();
+    MOZ_ASSERT(obj);
+    return obj;
+  }
+
+ private:
+  enum { OWNER_SLOT };
+
+  static const unsigned RESERVED_SLOTS = 1;
+
+  static const JSClassOps classOps_;
+
+  static const JSPropertySpec properties_[];
+  static const JSPropertySpec promiseProperties_[];
+  static const JSFunctionSpec methods_[];
+
+  PromiseObject* promise() const;
+
+  static MOZ_MUST_USE bool requireGlobal(JSContext* cx,
+                                         HandleDebuggerObject object);
+  static MOZ_MUST_USE bool requirePromise(JSContext* cx,
+                                          HandleDebuggerObject object);
+  static MOZ_MUST_USE bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+  struct PromiseReactionRecordBuilder;
+
+  static MOZ_MUST_USE bool getErrorReport(JSContext* cx,
+                                          HandleObject maybeError,
+                                          JSErrorReport*& report);
+};
+
+} /* namespace js */
+
+#endif /* debugger_Object_h */
diff --git a/js/src/debugger/Script-inl.h b/js/src/debugger/Script-inl.h
new file mode 100644
index 0000000000..909c714739
--- /dev/null
+++ b/js/src/debugger/Script-inl.h
@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Script_inl_h
+#define debugger_Script_inl_h
+
+#include "debugger/Script.h"  // for DebuggerScript
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+#include "mozilla/Variant.h"     // for AsVariant
+
+#include <utility>  // for move
+
+#include "jstypes.h"            // for JS_PUBLIC_API
+#include "debugger/Debugger.h"  // for DebuggerScriptReferent
+#include "gc/Cell.h"            // for Cell
+#include "vm/JSScript.h"        // for BaseScript, JSScript
+#include "vm/NativeObject.h"    // for NativeObject
+#include "wasm/WasmJS.h"        // for WasmInstanceObject
+
+#include "debugger/Debugger-inl.h"  // for Debugger::fromJSObject
+
+class JS_PUBLIC_API JSObject;
+
+// The Debugger.Script.prototype object also has a class of
+// DebuggerScript::class_ so we differentiate instances from the prototype
+// based on the presence of an owner debugger.
+inline bool js::DebuggerScript::isInstance() const {
+  return !getReservedSlot(OWNER_SLOT).isUndefined();
+}
+
+inline js::Debugger* js::DebuggerScript::owner() const {
+  MOZ_ASSERT(isInstance());
+  JSObject* dbgobj = &getReservedSlot(OWNER_SLOT).toObject();
+  return Debugger::fromJSObject(dbgobj);
+}
+
+js::gc::Cell* js::DebuggerScript::getReferentCell() const {
+  return static_cast<gc::Cell*>(getPrivate());
+}
+
+js::DebuggerScriptReferent js::DebuggerScript::getReferent() const {
+  if (gc::Cell* cell = getReferentCell()) {
+    if (cell->is<BaseScript>()) {
+      return mozilla::AsVariant(cell->as<BaseScript>());
+    }
+    MOZ_ASSERT(cell->is<JSObject>());
+    return mozilla::AsVariant(
+        &static_cast<NativeObject*>(cell)->as<WasmInstanceObject>());
+  }
+  return mozilla::AsVariant(static_cast<BaseScript*>(nullptr));
+}
+
+js::BaseScript* js::DebuggerScript::getReferentScript() const {
+  gc::Cell* cell = getReferentCell();
+  return cell->as<BaseScript>();
+}
+
+#endif /* debugger_Script_inl_h */
diff --git a/js/src/debugger/Script.cpp b/js/src/debugger/Script.cpp
new file mode 100644
index 0000000000..9da715bee3
--- /dev/null
+++ b/js/src/debugger/Script.cpp
@@ -0,0 +1,2369 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Script-inl.h"
+
+#include "mozilla/Maybe.h"   // for Some, Maybe
+#include "mozilla/Span.h"    // for Span
+#include "mozilla/Vector.h"  // for Vector
+
+#include <stddef.h>  // for ptrdiff_t
+#include <stdint.h>  // for uint32_t, SIZE_MAX, int32_t
+
+#include "jsapi.h"             // for CallArgs, Rooted, CallArgsFromVp
+#include "jsnum.h"             // for ToNumber
+#include "NamespaceImports.h"  // for CallArgs, RootedValue
+
+#include "builtin/Array.h"         // for NewDenseEmptyArray
+#include "debugger/Debugger.h"     // for DebuggerScriptReferent, Debugger
+#include "debugger/DebugScript.h"  // for DebugScript
+#include "debugger/Source.h"       // for DebuggerSource
+#include "gc/Barrier.h"            // for ImmutablePropertyNamePtr
+#include "gc/GC.h"                 // for MemoryUse, MemoryUse::Breakpoint
+#include "gc/Rooting.h"            // for RootedDebuggerScript
+#include "gc/Tracer.h"         // for TraceManuallyBarrieredCrossCompartmentEdge
+#include "gc/Zone.h"           // for Zone
+#include "gc/ZoneAllocator.h"  // for AddCellMemory
+#include "js/friend/ErrorMessages.h"  // for GetErrorMessage, JSMSG_*
+#include "js/HeapAPI.h"               // for GCCellPtr
+#include "js/Wrapper.h"               // for UncheckedUnwrap
+#include "vm/ArrayObject.h"           // for ArrayObject
+#include "vm/BytecodeUtil.h"          // for GET_JUMP_OFFSET
+#include "vm/GlobalObject.h"          // for GlobalObject
+#include "vm/JSContext.h"             // for JSContext, ReportValueError
+#include "vm/JSFunction.h"            // for JSFunction
+#include "vm/JSObject.h"              // for RequireObject, JSObject
+#include "vm/ObjectOperations.h"      // for DefineDataProperty, HasOwnProperty
+#include "vm/PlainObject.h"           // for js::PlainObject
+#include "vm/Realm.h"                 // for AutoRealm
+#include "vm/Runtime.h"               // for JSAtomState, JSRuntime
+#include "vm/StringType.h"            // for NameToId, PropertyName, JSAtom
+#include "wasm/WasmDebug.h"           // for ExprLoc, DebugState
+#include "wasm/WasmInstance.h"        // for Instance
+#include "wasm/WasmTypes.h"           // for Bytes
+
+#include "vm/BytecodeUtil-inl.h"  // for BytecodeRangeWithPosition
+#include "vm/JSAtom-inl.h"        // for ValueToId
+#include "vm/JSObject-inl.h"  // for NewBuiltinClassInstance, NewObjectWithGivenProto, NewTenuredObjectWithGivenProto
+#include "vm/JSScript-inl.h"  // for JSScript::global
+#include "vm/ObjectOperations-inl.h"  // for GetProperty
+#include "vm/Realm-inl.h"             // for AutoRealm::AutoRealm
+
+using namespace js;
+
+using mozilla::Maybe;
+using mozilla::Some;
+
+const JSClassOps DebuggerScript::classOps_ = {
+    nullptr,                          // addProperty
+    nullptr,                          // delProperty
+    nullptr,                          // enumerate
+    nullptr,                          // newEnumerate
+    nullptr,                          // resolve
+    nullptr,                          // mayResolve
+    nullptr,                          // finalize
+    nullptr,                          // call
+    nullptr,                          // hasInstance
+    nullptr,                          // construct
+    CallTraceMethod<DebuggerScript>,  // trace
+};
+
+const JSClass DebuggerScript::class_ = {
+    "Script", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS),
+    &classOps_};
+
+void DebuggerScript::trace(JSTracer* trc) {
+  JSObject* upcast = this;
+  // This comes from a private pointer, so no barrier needed.
+  gc::Cell* cell = getReferentCell();
+  if (cell) {
+    if (cell->is<BaseScript>()) {
+      BaseScript* script = cell->as<BaseScript>();
+      TraceManuallyBarrieredCrossCompartmentEdge(
+          trc, upcast, &script, "Debugger.Script script referent");
+      setPrivateUnbarriered(script);
+    } else {
+      JSObject* wasm = cell->as<JSObject>();
+      TraceManuallyBarrieredCrossCompartmentEdge(
+          trc, upcast, &wasm, "Debugger.Script wasm referent");
+      MOZ_ASSERT(wasm->is<WasmInstanceObject>());
+      setPrivateUnbarriered(wasm);
+    }
+  }
+}
+
+/* static */
+NativeObject* DebuggerScript::initClass(JSContext* cx,
+                                        Handle<GlobalObject*> global,
+                                        HandleObject debugCtor) {
+  return InitClass(cx, debugCtor, nullptr, &class_, construct, 0, properties_,
+                   methods_, nullptr, nullptr);
+}
+
+/* static */
+DebuggerScript* DebuggerScript::create(JSContext* cx, HandleObject proto,
+                                       Handle<DebuggerScriptReferent> referent,
+                                       HandleNativeObject debugger) {
+  DebuggerScript* scriptobj =
+      NewTenuredObjectWithGivenProto<DebuggerScript>(cx, proto);
+  if (!scriptobj) {
+    return nullptr;
+  }
+
+  scriptobj->setReservedSlot(DebuggerScript::OWNER_SLOT,
+                             ObjectValue(*debugger));
+  referent.get().match(
+      [&](auto& scriptHandle) { scriptobj->setPrivateGCThing(scriptHandle); });
+
+  return scriptobj;
+}
+
+static JSScript* DelazifyScript(JSContext* cx, Handle<BaseScript*> script) {
+  if (script->hasBytecode()) {
+    return script->asJSScript();
+  }
+  MOZ_ASSERT(script->isFunction());
+
+  // JSFunction::getOrCreateScript requires an enclosing scope. This requires
+  // the enclosing script to be non-lazy.
+  if (script->hasEnclosingScript()) {
+    Rooted<BaseScript*> enclosingScript(cx, script->enclosingScript());
+    if (!DelazifyScript(cx, enclosingScript)) {
+      return nullptr;
+    }
+
+    if (!script->isReadyForDelazification()) {
+      // It didn't work! Delazifying the enclosing script still didn't
+      // delazify this script. This happens when the function
+      // corresponding to this script was removed by constant folding.
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_OPTIMIZED_OUT_FUN);
+      return nullptr;
+    }
+  }
+
+  MOZ_ASSERT(script->enclosingScope());
+
+  RootedFunction fun(cx, script->function());
+  AutoRealm ar(cx, fun);
+  return JSFunction::getOrCreateScript(cx, fun);
+}
+
+/* static */
+DebuggerScript* DebuggerScript::check(JSContext* cx, HandleValue v) {
+  JSObject* thisobj = RequireObject(cx, v);
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerScript>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Script",
+                              "method", thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  DebuggerScript& scriptObj = thisobj->as<DebuggerScript>();
+
+  // Check for Debugger.Script.prototype, which is of class
+  // DebuggerScript::class.
+  if (!scriptObj.isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Script",
+                              "method", "prototype object");
+    return nullptr;
+  }
+
+  return &scriptObj;
+}
+
+struct MOZ_STACK_CLASS DebuggerScript::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  HandleDebuggerScript obj;
+  Rooted<DebuggerScriptReferent> referent;
+  RootedScript script;
+
+  CallData(JSContext* cx, const CallArgs& args, HandleDebuggerScript obj)
+      : cx(cx),
+        args(args),
+        obj(obj),
+        referent(cx, obj->getReferent()),
+        script(cx) {}
+
+  MOZ_MUST_USE bool ensureScriptMaybeLazy() {
+    if (!referent.is<BaseScript*>()) {
+      ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK,
+                       args.thisv(), nullptr, "a JS script");
+      return false;
+    }
+    return true;
+  }
+
+  MOZ_MUST_USE bool ensureScript() {
+    if (!ensureScriptMaybeLazy()) {
+      return false;
+    }
+    script = DelazifyScript(cx, referent.as<BaseScript*>());
+    if (!script) {
+      return false;
+    }
+    return true;
+  }
+
+  bool getIsGeneratorFunction();
+  bool getIsAsyncFunction();
+  bool getIsFunction();
+  bool getIsModule();
+  bool getDisplayName();
+  bool getParameterNames();
+  bool getUrl();
+  bool getStartLine();
+  bool getStartColumn();
+  bool getLineCount();
+  bool getSource();
+  bool getSourceStart();
+  bool getSourceLength();
+  bool getMainOffset();
+  bool getGlobal();
+  bool getFormat();
+  bool getChildScripts();
+  bool getPossibleBreakpoints();
+  bool getPossibleBreakpointOffsets();
+  bool getOffsetMetadata();
+  bool getOffsetLocation();
+  bool getEffectfulOffsets();
+  bool getAllOffsets();
+  bool getAllColumnOffsets();
+  bool getLineOffsets();
+  bool setBreakpoint();
+  bool getBreakpoints();
+  bool clearBreakpoint();
+  bool clearAllBreakpoints();
+  bool isInCatchScope();
+  bool getOffsetsCoverage();
+  bool setInstrumentationId();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <DebuggerScript::CallData::Method MyMethod>
+/* static */
+bool DebuggerScript::CallData::ToNative(JSContext* cx, unsigned argc,
+                                        Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedDebuggerScript obj(cx, DebuggerScript::check(cx, args.thisv()));
+  if (!obj) {
+    return false;
+  }
+
+  CallData data(cx, args, obj);
+  return (data.*MyMethod)();
+}
+
+bool DebuggerScript::CallData::getIsGeneratorFunction() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  args.rval().setBoolean(obj->getReferentScript()->isGenerator());
+  return true;
+}
+
+bool DebuggerScript::CallData::getIsAsyncFunction() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  args.rval().setBoolean(obj->getReferentScript()->isAsync());
+  return true;
+}
+
+bool DebuggerScript::CallData::getIsFunction() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+
+  args.rval().setBoolean(obj->getReferentScript()->function());
+  return true;
+}
+
+bool DebuggerScript::CallData::getIsModule() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  BaseScript* script = referent.as<BaseScript*>();
+
+  args.rval().setBoolean(script->isModule());
+  return true;
+}
+
+bool DebuggerScript::CallData::getDisplayName() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  JSFunction* func = obj->getReferentScript()->function();
+  Debugger* dbg = obj->owner();
+
+  JSString* name = func ? func->displayAtom() : nullptr;
+  if (!name) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  RootedValue namev(cx, StringValue(name));
+  if (!dbg->wrapDebuggeeValue(cx, &namev)) {
+    return false;
+  }
+  args.rval().set(namev);
+  return true;
+}
+
+bool DebuggerScript::CallData::getParameterNames() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+
+  RootedFunction fun(cx, referent.as<BaseScript*>()->function());
+  if (!fun) {
+    args.rval().setUndefined();
+    return true;
+  }
+
+  ArrayObject* arr = GetFunctionParameterNamesArray(cx, fun);
+  if (!arr) {
+    return false;
+  }
+
+  args.rval().setObject(*arr);
+  return true;
+}
+
+bool DebuggerScript::CallData::getUrl() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+
+  Rooted<BaseScript*> script(cx, referent.as<BaseScript*>());
+
+  if (script->filename()) {
+    JSString* str;
+    if (script->scriptSource()->introducerFilename()) {
+      str = NewStringCopyZ<CanGC>(cx,
+                                  script->scriptSource()->introducerFilename());
+    } else {
+      str = NewStringCopyZ<CanGC>(cx, script->filename());
+    }
+    if (!str) {
+      return false;
+    }
+    args.rval().setString(str);
+  } else {
+    args.rval().setNull();
+  }
+  return true;
+}
+
+bool DebuggerScript::CallData::getStartLine() {
+  args.rval().setNumber(
+      referent.get().match([](BaseScript*& s) { return s->lineno(); },
+                           [](WasmInstanceObject*&) { return (uint32_t)1; }));
+  return true;
+}
+
+bool DebuggerScript::CallData::getStartColumn() {
+  args.rval().setNumber(
+      referent.get().match([](BaseScript*& s) { return s->column(); },
+                           [](WasmInstanceObject*&) { return (uint32_t)0; }));
+  return true;
+}
+
+struct DebuggerScript::GetLineCountMatcher {
+  JSContext* cx_;
+  double totalLines;
+
+  explicit GetLineCountMatcher(JSContext* cx) : cx_(cx), totalLines(0.0) {}
+  using ReturnType = bool;
+
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+    totalLines = double(GetScriptLineExtent(script));
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    if (instance.debugEnabled()) {
+      totalLines = double(instance.debug().bytecode().length());
+    } else {
+      totalLines = 0;
+    }
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getLineCount() {
+  GetLineCountMatcher matcher(cx);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+  args.rval().setNumber(matcher.totalLines);
+  return true;
+}
+
+class DebuggerScript::GetSourceMatcher {
+  JSContext* cx_;
+  Debugger* dbg_;
+
+ public:
+  GetSourceMatcher(JSContext* cx, Debugger* dbg) : cx_(cx), dbg_(dbg) {}
+
+  using ReturnType = DebuggerSource*;
+
+  ReturnType match(Handle<BaseScript*> script) {
+    RootedScriptSourceObject source(cx_, script->sourceObject());
+    return dbg_->wrapSource(cx_, source);
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    return dbg_->wrapWasmSource(cx_, wasmInstance);
+  }
+};
+
+bool DebuggerScript::CallData::getSource() {
+  Debugger* dbg = obj->owner();
+
+  GetSourceMatcher matcher(cx, dbg);
+  RootedDebuggerSource sourceObject(cx, referent.match(matcher));
+  if (!sourceObject) {
+    return false;
+  }
+
+  args.rval().setObject(*sourceObject);
+  return true;
+}
+
+bool DebuggerScript::CallData::getSourceStart() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  args.rval().setNumber(uint32_t(obj->getReferentScript()->sourceStart()));
+  return true;
+}
+
+bool DebuggerScript::CallData::getSourceLength() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  args.rval().setNumber(uint32_t(obj->getReferentScript()->sourceLength()));
+  return true;
+}
+
+bool DebuggerScript::CallData::getMainOffset() {
+  if (!ensureScript()) {
+    return false;
+  }
+  args.rval().setNumber(uint32_t(script->mainOffset()));
+  return true;
+}
+
+bool DebuggerScript::CallData::getGlobal() {
+  if (!ensureScript()) {
+    return false;
+  }
+  Debugger* dbg = obj->owner();
+
+  RootedValue v(cx, ObjectValue(script->global()));
+  if (!dbg->wrapDebuggeeValue(cx, &v)) {
+    return false;
+  }
+  args.rval().set(v);
+  return true;
+}
+
+bool DebuggerScript::CallData::getFormat() {
+  args.rval().setString(referent.get().match(
+      [=](BaseScript*&) { return cx->names().js.get(); },
+      [=](WasmInstanceObject*&) { return cx->names().wasm.get(); }));
+  return true;
+}
+
+static bool PushFunctionScript(JSContext* cx, Debugger* dbg, HandleFunction fun,
+                               HandleObject array) {
+  // Ignore asm.js natives.
+  if (!IsInterpretedNonSelfHostedFunction(fun)) {
+    return true;
+  }
+
+  Rooted<BaseScript*> script(cx, fun->baseScript());
+  RootedObject wrapped(cx, dbg->wrapScript(cx, script));
+  if (!wrapped) {
+    return false;
+  }
+
+  return NewbornArrayPush(cx, array, ObjectValue(*wrapped));
+}
+
+static bool PushInnerFunctions(JSContext* cx, Debugger* dbg, HandleObject array,
+                               mozilla::Span<const JS::GCCellPtr> gcThings) {
+  RootedFunction fun(cx);
+
+  for (JS::GCCellPtr gcThing : gcThings) {
+    if (!gcThing.is<JSObject>()) {
+      continue;
+    }
+
+    JSObject* obj = &gcThing.as<JSObject>();
+    if (obj->is<JSFunction>()) {
+      fun = &obj->as<JSFunction>();
+
+      if (!PushFunctionScript(cx, dbg, fun, array)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+bool DebuggerScript::CallData::getChildScripts() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+  Debugger* dbg = obj->owner();
+
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+
+  Rooted<BaseScript*> script(cx, obj->getReferent().as<BaseScript*>());
+  if (!PushInnerFunctions(cx, dbg, result, script->gcthings())) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+static bool ScriptOffset(JSContext* cx, const Value& v, size_t* offsetp) {
+  double d;
+  size_t off;
+
+  bool ok = v.isNumber();
+  if (ok) {
+    d = v.toNumber();
+    off = size_t(d);
+  }
+  if (!ok || off != d) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_BAD_OFFSET);
+    return false;
+  }
+  *offsetp = off;
+  return true;
+}
+
+static bool EnsureScriptOffsetIsValid(JSContext* cx, JSScript* script,
+                                      size_t offset) {
+  if (IsValidBytecodeOffset(cx, script, offset)) {
+    return true;
+  }
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                            JSMSG_DEBUG_BAD_OFFSET);
+  return false;
+}
+
+template <bool OnlyOffsets>
+class DebuggerScript::GetPossibleBreakpointsMatcher {
+  JSContext* cx_;
+  MutableHandleObject result_;
+
+  Maybe<size_t> minOffset;
+  Maybe<size_t> maxOffset;
+
+  Maybe<size_t> minLine;
+  size_t minColumn;
+  Maybe<size_t> maxLine;
+  size_t maxColumn;
+
+  bool passesQuery(size_t offset, size_t lineno, size_t colno) {
+    // [minOffset, maxOffset) - Inclusive minimum and exclusive maximum.
+    if ((minOffset && offset < *minOffset) ||
+        (maxOffset && offset >= *maxOffset)) {
+      return false;
+    }
+
+    if (minLine) {
+      if (lineno < *minLine || (lineno == *minLine && colno < minColumn)) {
+        return false;
+      }
+    }
+
+    if (maxLine) {
+      if (lineno > *maxLine || (lineno == *maxLine && colno >= maxColumn)) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  bool maybeAppendEntry(size_t offset, size_t lineno, size_t colno,
+                        bool isStepStart) {
+    if (!passesQuery(offset, lineno, colno)) {
+      return true;
+    }
+
+    if (OnlyOffsets) {
+      if (!NewbornArrayPush(cx_, result_, NumberValue(offset))) {
+        return false;
+      }
+
+      return true;
+    }
+
+    RootedPlainObject entry(cx_, NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!entry) {
+      return false;
+    }
+
+    RootedValue value(cx_, NumberValue(offset));
+    if (!DefineDataProperty(cx_, entry, cx_->names().offset, value)) {
+      return false;
+    }
+
+    value = NumberValue(lineno);
+    if (!DefineDataProperty(cx_, entry, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(colno);
+    if (!DefineDataProperty(cx_, entry, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    value = BooleanValue(isStepStart);
+    if (!DefineDataProperty(cx_, entry, cx_->names().isStepStart, value)) {
+      return false;
+    }
+
+    if (!NewbornArrayPush(cx_, result_, ObjectValue(*entry))) {
+      return false;
+    }
+    return true;
+  }
+
+  bool parseIntValue(HandleValue value, size_t* result) {
+    if (!value.isNumber()) {
+      return false;
+    }
+
+    double doubleOffset = value.toNumber();
+    if (doubleOffset < 0 || (unsigned int)doubleOffset != doubleOffset) {
+      return false;
+    }
+
+    *result = doubleOffset;
+    return true;
+  }
+
+  bool parseIntValue(HandleValue value, Maybe<size_t>* result) {
+    size_t result_;
+    if (!parseIntValue(value, &result_)) {
+      return false;
+    }
+
+    *result = Some(result_);
+    return true;
+  }
+
+ public:
+  explicit GetPossibleBreakpointsMatcher(JSContext* cx,
+                                         MutableHandleObject result)
+      : cx_(cx),
+        result_(result),
+        minOffset(),
+        maxOffset(),
+        minLine(),
+        minColumn(0),
+        maxLine(),
+        maxColumn(0) {}
+
+  bool parseQuery(HandleObject query) {
+    RootedValue lineValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().line, &lineValue)) {
+      return false;
+    }
+
+    RootedValue minLineValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().minLine, &minLineValue)) {
+      return false;
+    }
+
+    RootedValue minColumnValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().minColumn,
+                     &minColumnValue)) {
+      return false;
+    }
+
+    RootedValue minOffsetValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().minOffset,
+                     &minOffsetValue)) {
+      return false;
+    }
+
+    RootedValue maxLineValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().maxLine, &maxLineValue)) {
+      return false;
+    }
+
+    RootedValue maxColumnValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().maxColumn,
+                     &maxColumnValue)) {
+      return false;
+    }
+
+    RootedValue maxOffsetValue(cx_);
+    if (!GetProperty(cx_, query, query, cx_->names().maxOffset,
+                     &maxOffsetValue)) {
+      return false;
+    }
+
+    if (!minOffsetValue.isUndefined()) {
+      if (!parseIntValue(minOffsetValue, &minOffset)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'minOffset'", "not an integer");
+        return false;
+      }
+    }
+    if (!maxOffsetValue.isUndefined()) {
+      if (!parseIntValue(maxOffsetValue, &maxOffset)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'maxOffset'", "not an integer");
+        return false;
+      }
+    }
+
+    if (!lineValue.isUndefined()) {
+      if (!minLineValue.isUndefined() || !maxLineValue.isUndefined()) {
+        JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                  JSMSG_UNEXPECTED_TYPE,
+                                  "getPossibleBreakpoints' 'line'",
+                                  "not allowed alongside 'minLine'/'maxLine'");
+        return false;
+      }
+
+      size_t line;
+      if (!parseIntValue(lineValue, &line)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'line'", "not an integer");
+        return false;
+      }
+
+      // If no end column is given, we use the default of 0 and wrap to
+      // the next line.
+      minLine = Some(line);
+      maxLine = Some(line + (maxColumnValue.isUndefined() ? 1 : 0));
+    }
+
+    if (!minLineValue.isUndefined()) {
+      if (!parseIntValue(minLineValue, &minLine)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'minLine'", "not an integer");
+        return false;
+      }
+    }
+
+    if (!minColumnValue.isUndefined()) {
+      if (!minLine) {
+        JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                  JSMSG_UNEXPECTED_TYPE,
+                                  "getPossibleBreakpoints' 'minColumn'",
+                                  "not allowed without 'line' or 'minLine'");
+        return false;
+      }
+
+      if (!parseIntValue(minColumnValue, &minColumn)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'minColumn'", "not an integer");
+        return false;
+      }
+    }
+
+    if (!maxLineValue.isUndefined()) {
+      if (!parseIntValue(maxLineValue, &maxLine)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'maxLine'", "not an integer");
+        return false;
+      }
+    }
+
+    if (!maxColumnValue.isUndefined()) {
+      if (!maxLine) {
+        JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                  JSMSG_UNEXPECTED_TYPE,
+                                  "getPossibleBreakpoints' 'maxColumn'",
+                                  "not allowed without 'line' or 'maxLine'");
+        return false;
+      }
+
+      if (!parseIntValue(maxColumnValue, &maxColumn)) {
+        JS_ReportErrorNumberASCII(
+            cx_, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+            "getPossibleBreakpoints' 'maxColumn'", "not an integer");
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  using ReturnType = bool;
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    // Second pass: build the result array.
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    for (BytecodeRangeWithPosition r(cx_, script); !r.empty(); r.popFront()) {
+      if (!r.frontIsBreakablePoint()) {
+        continue;
+      }
+
+      size_t offset = r.frontOffset();
+      size_t lineno = r.frontLineNumber();
+      size_t colno = r.frontColumnNumber();
+
+      if (!maybeAppendEntry(offset, lineno, colno,
+                            r.frontIsBreakableStepPoint())) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+
+    Vector<wasm::ExprLoc> offsets(cx_);
+    if (instance.debugEnabled() &&
+        !instance.debug().getAllColumnOffsets(&offsets)) {
+      return false;
+    }
+
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    for (uint32_t i = 0; i < offsets.length(); i++) {
+      size_t lineno = offsets[i].lineno;
+      size_t column = offsets[i].column;
+      size_t offset = offsets[i].offset;
+      if (!maybeAppendEntry(offset, lineno, column, true)) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getPossibleBreakpoints() {
+  RootedObject result(cx);
+  GetPossibleBreakpointsMatcher<false> matcher(cx, &result);
+  if (args.length() >= 1 && !args[0].isUndefined()) {
+    RootedObject queryObject(cx, RequireObject(cx, args[0]));
+    if (!queryObject || !matcher.parseQuery(queryObject)) {
+      return false;
+    }
+  }
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerScript::CallData::getPossibleBreakpointOffsets() {
+  RootedObject result(cx);
+  GetPossibleBreakpointsMatcher<true> matcher(cx, &result);
+  if (args.length() >= 1 && !args[0].isUndefined()) {
+    RootedObject queryObject(cx, RequireObject(cx, args[0]));
+    if (!queryObject || !matcher.parseQuery(queryObject)) {
+      return false;
+    }
+  }
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+class DebuggerScript::GetOffsetMetadataMatcher {
+  JSContext* cx_;
+  size_t offset_;
+  MutableHandlePlainObject result_;
+
+ public:
+  explicit GetOffsetMetadataMatcher(JSContext* cx, size_t offset,
+                                    MutableHandlePlainObject result)
+      : cx_(cx), offset_(offset), result_(result) {}
+  using ReturnType = bool;
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    if (!EnsureScriptOffsetIsValid(cx_, script, offset_)) {
+      return false;
+    }
+
+    result_.set(NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    BytecodeRangeWithPosition r(cx_, script);
+    while (!r.empty() && r.frontOffset() < offset_) {
+      r.popFront();
+    }
+
+    RootedValue value(cx_, NumberValue(r.frontLineNumber()));
+    if (!DefineDataProperty(cx_, result_, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(r.frontColumnNumber());
+    if (!DefineDataProperty(cx_, result_, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    value = BooleanValue(r.frontIsBreakablePoint());
+    if (!DefineDataProperty(cx_, result_, cx_->names().isBreakpoint, value)) {
+      return false;
+    }
+
+    value = BooleanValue(r.frontIsBreakableStepPoint());
+    if (!DefineDataProperty(cx_, result_, cx_->names().isStepStart, value)) {
+      return false;
+    }
+
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    if (!instance.debugEnabled()) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_OFFSET);
+      return false;
+    }
+
+    size_t lineno;
+    size_t column;
+    if (!instance.debug().getOffsetLocation(offset_, &lineno, &column)) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_OFFSET);
+      return false;
+    }
+
+    result_.set(NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    RootedValue value(cx_, NumberValue(lineno));
+    if (!DefineDataProperty(cx_, result_, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(column);
+    if (!DefineDataProperty(cx_, result_, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    value.setBoolean(true);
+    if (!DefineDataProperty(cx_, result_, cx_->names().isBreakpoint, value)) {
+      return false;
+    }
+
+    value.setBoolean(true);
+    if (!DefineDataProperty(cx_, result_, cx_->names().isStepStart, value)) {
+      return false;
+    }
+
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getOffsetMetadata() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.getOffsetMetadata", 1)) {
+    return false;
+  }
+  size_t offset;
+  if (!ScriptOffset(cx, args[0], &offset)) {
+    return false;
+  }
+
+  RootedPlainObject result(cx);
+  GetOffsetMetadataMatcher matcher(cx, offset, &result);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+namespace {
+
+/*
+ * FlowGraphSummary::populate(cx, script) computes a summary of script's
+ * control flow graph used by DebuggerScript_{getAllOffsets,getLineOffsets}.
+ *
+ * An instruction on a given line is an entry point for that line if it can be
+ * reached from (an instruction on) a different line. We distinguish between the
+ * following cases:
+ *   - hasNoEdges:
+ *       The instruction cannot be reached, so the instruction is not an entry
+ *       point for the line it is on.
+ *   - hasSingleEdge:
+ *       The instruction can be reached from a single line. If this line is
+ *       different from the line the instruction is on, the instruction is an
+ *       entry point for that line.
+ *
+ * Similarly, an instruction on a given position (line/column pair) is an
+ * entry point for that position if it can be reached from (an instruction on) a
+ * different position. Again, we distinguish between the following cases:
+ *   - hasNoEdges:
+ *       The instruction cannot be reached, so the instruction is not an entry
+ *       point for the position it is on.
+ *   - hasSingleEdge:
+ *       The instruction can be reached from a single position. If this line is
+ *       different from the position the instruction is on, the instruction is
+ *       an entry point for that position.
+ */
+class FlowGraphSummary {
+ public:
+  class Entry {
+   public:
+    static Entry createWithSingleEdge(size_t lineno, size_t column) {
+      return Entry(lineno, column);
+    }
+
+    static Entry createWithMultipleEdgesFromSingleLine(size_t lineno) {
+      return Entry(lineno, SIZE_MAX);
+    }
+
+    static Entry createWithMultipleEdgesFromMultipleLines() {
+      return Entry(SIZE_MAX, SIZE_MAX);
+    }
+
+    Entry() : lineno_(SIZE_MAX), column_(0) {}
+
+    bool hasNoEdges() const {
+      return lineno_ == SIZE_MAX && column_ != SIZE_MAX;
+    }
+
+    bool hasSingleEdge() const {
+      return lineno_ != SIZE_MAX && column_ != SIZE_MAX;
+    }
+
+    size_t lineno() const { return lineno_; }
+
+    size_t column() const { return column_; }
+
+   private:
+    Entry(size_t lineno, size_t column) : lineno_(lineno), column_(column) {}
+
+    size_t lineno_;
+    size_t column_;
+  };
+
+  explicit FlowGraphSummary(JSContext* cx) : entries_(cx) {}
+
+  Entry& operator[](size_t index) { return entries_[index]; }
+
+  bool populate(JSContext* cx, JSScript* script) {
+    if (!entries_.growBy(script->length())) {
+      return false;
+    }
+    unsigned mainOffset = script->pcToOffset(script->main());
+    entries_[mainOffset] = Entry::createWithMultipleEdgesFromMultipleLines();
+
+    size_t prevLineno = script->lineno();
+    size_t prevColumn = 0;
+    JSOp prevOp = JSOp::Nop;
+    for (BytecodeRangeWithPosition r(cx, script); !r.empty(); r.popFront()) {
+      size_t lineno = prevLineno;
+      size_t column = prevColumn;
+      JSOp op = r.frontOpcode();
+
+      if (BytecodeFallsThrough(prevOp)) {
+        addEdge(prevLineno, prevColumn, r.frontOffset());
+      }
+
+      // If we visit the branch target before we visit the
+      // branch op itself, just reuse the previous location.
+      // This is reasonable for the time being because this
+      // situation can currently only arise from loop heads,
+      // where this assumption holds.
+      if (BytecodeIsJumpTarget(op) && !entries_[r.frontOffset()].hasNoEdges()) {
+        lineno = entries_[r.frontOffset()].lineno();
+        column = entries_[r.frontOffset()].column();
+      }
+
+      if (r.frontIsEntryPoint()) {
+        lineno = r.frontLineNumber();
+        column = r.frontColumnNumber();
+      }
+
+      if (IsJumpOpcode(op)) {
+        addEdge(lineno, column, r.frontOffset() + GET_JUMP_OFFSET(r.frontPC()));
+      } else if (op == JSOp::TableSwitch) {
+        jsbytecode* const switchPC = r.frontPC();
+        jsbytecode* pc = switchPC;
+        size_t offset = r.frontOffset();
+        ptrdiff_t step = JUMP_OFFSET_LEN;
+        size_t defaultOffset = offset + GET_JUMP_OFFSET(pc);
+        pc += step;
+        addEdge(lineno, column, defaultOffset);
+
+        int32_t low = GET_JUMP_OFFSET(pc);
+        pc += JUMP_OFFSET_LEN;
+        int ncases = GET_JUMP_OFFSET(pc) - low + 1;
+        pc += JUMP_OFFSET_LEN;
+
+        for (int i = 0; i < ncases; i++) {
+          size_t target = script->tableSwitchCaseOffset(switchPC, i);
+          addEdge(lineno, column, target);
+        }
+      } else if (op == JSOp::Try) {
+        // As there is no literal incoming edge into the catch block, we
+        // make a fake one by copying the JSOp::Try location, as-if this
+        // was an incoming edge of the catch block. This is needed
+        // because we only report offsets of entry points which have
+        // valid incoming edges.
+        for (const TryNote& tn : script->trynotes()) {
+          if (tn.start == r.frontOffset() + JSOpLength_Try) {
+            uint32_t catchOffset = tn.start + tn.length;
+            if (tn.kind() == TryNoteKind::Catch ||
+                tn.kind() == TryNoteKind::Finally) {
+              addEdge(lineno, column, catchOffset);
+            }
+          }
+        }
+      }
+
+      prevLineno = lineno;
+      prevColumn = column;
+      prevOp = op;
+    }
+
+    return true;
+  }
+
+ private:
+  void addEdge(size_t sourceLineno, size_t sourceColumn, size_t targetOffset) {
+    if (entries_[targetOffset].hasNoEdges()) {
+      entries_[targetOffset] =
+          Entry::createWithSingleEdge(sourceLineno, sourceColumn);
+    } else if (entries_[targetOffset].lineno() != sourceLineno) {
+      entries_[targetOffset] =
+          Entry::createWithMultipleEdgesFromMultipleLines();
+    } else if (entries_[targetOffset].column() != sourceColumn) {
+      entries_[targetOffset] =
+          Entry::createWithMultipleEdgesFromSingleLine(sourceLineno);
+    }
+  }
+
+  Vector<Entry> entries_;
+};
+
+} /* anonymous namespace */
+
+class DebuggerScript::GetOffsetLocationMatcher {
+  JSContext* cx_;
+  size_t offset_;
+  MutableHandlePlainObject result_;
+
+ public:
+  explicit GetOffsetLocationMatcher(JSContext* cx, size_t offset,
+                                    MutableHandlePlainObject result)
+      : cx_(cx), offset_(offset), result_(result) {}
+  using ReturnType = bool;
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    if (!EnsureScriptOffsetIsValid(cx_, script, offset_)) {
+      return false;
+    }
+
+    FlowGraphSummary flowData(cx_);
+    if (!flowData.populate(cx_, script)) {
+      return false;
+    }
+
+    result_.set(NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    BytecodeRangeWithPosition r(cx_, script);
+    while (!r.empty() && r.frontOffset() < offset_) {
+      r.popFront();
+    }
+
+    size_t offset = r.frontOffset();
+    bool isEntryPoint = r.frontIsEntryPoint();
+
+    // Line numbers are only correctly defined on entry points. Thus looks
+    // either for the next valid offset in the flowData, being the last entry
+    // point flowing into the current offset, or for the next valid entry point.
+    while (!r.frontIsEntryPoint() &&
+           !flowData[r.frontOffset()].hasSingleEdge()) {
+      r.popFront();
+      MOZ_ASSERT(!r.empty());
+    }
+
+    // If this is an entry point, take the line number associated with the entry
+    // point, otherwise settle on the next instruction and take the incoming
+    // edge position.
+    size_t lineno;
+    size_t column;
+    if (r.frontIsEntryPoint()) {
+      lineno = r.frontLineNumber();
+      column = r.frontColumnNumber();
+    } else {
+      MOZ_ASSERT(flowData[r.frontOffset()].hasSingleEdge());
+      lineno = flowData[r.frontOffset()].lineno();
+      column = flowData[r.frontOffset()].column();
+    }
+
+    RootedValue value(cx_, NumberValue(lineno));
+    if (!DefineDataProperty(cx_, result_, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(column);
+    if (!DefineDataProperty(cx_, result_, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    // The same entry point test that is used by getAllColumnOffsets.
+    isEntryPoint = (isEntryPoint && !flowData[offset].hasNoEdges() &&
+                    (flowData[offset].lineno() != r.frontLineNumber() ||
+                     flowData[offset].column() != r.frontColumnNumber()));
+    value.setBoolean(isEntryPoint);
+    if (!DefineDataProperty(cx_, result_, cx_->names().isEntryPoint, value)) {
+      return false;
+    }
+
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    if (!instance.debugEnabled()) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_OFFSET);
+      return false;
+    }
+
+    size_t lineno;
+    size_t column;
+    if (!instance.debug().getOffsetLocation(offset_, &lineno, &column)) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_OFFSET);
+      return false;
+    }
+
+    result_.set(NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    RootedValue value(cx_, NumberValue(lineno));
+    if (!DefineDataProperty(cx_, result_, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(column);
+    if (!DefineDataProperty(cx_, result_, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    value.setBoolean(true);
+    if (!DefineDataProperty(cx_, result_, cx_->names().isEntryPoint, value)) {
+      return false;
+    }
+
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getOffsetLocation() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.getOffsetLocation", 1)) {
+    return false;
+  }
+  size_t offset;
+  if (!ScriptOffset(cx, args[0], &offset)) {
+    return false;
+  }
+
+  RootedPlainObject result(cx);
+  GetOffsetLocationMatcher matcher(cx, offset, &result);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+// Return whether an opcode is considered effectful: it can have direct side
+// effects that can be observed outside of the current frame. Opcodes are not
+// effectful if they only modify the current frame's state, modify objects
+// created by the current frame, or can potentially call other scripts or
+// natives which could have side effects.
+static bool BytecodeIsEffectful(JSOp op) {
+  switch (op) {
+    case JSOp::SetProp:
+    case JSOp::StrictSetProp:
+    case JSOp::SetPropSuper:
+    case JSOp::StrictSetPropSuper:
+    case JSOp::SetElem:
+    case JSOp::StrictSetElem:
+    case JSOp::SetElemSuper:
+    case JSOp::StrictSetElemSuper:
+    case JSOp::SetName:
+    case JSOp::StrictSetName:
+    case JSOp::SetGName:
+    case JSOp::StrictSetGName:
+    case JSOp::DelProp:
+    case JSOp::StrictDelProp:
+    case JSOp::DelElem:
+    case JSOp::StrictDelElem:
+    case JSOp::DelName:
+    case JSOp::SetAliasedVar:
+    case JSOp::InitHomeObject:
+    case JSOp::InitAliasedLexical:
+    case JSOp::SetIntrinsic:
+    case JSOp::InitGLexical:
+    case JSOp::GlobalOrEvalDeclInstantiation:
+    case JSOp::SetFunName:
+    case JSOp::MutateProto:
+    case JSOp::DynamicImport:
+      // Treat async functions as effectful so that microtask checkpoints
+      // won't run.
+    case JSOp::InitialYield:
+    case JSOp::Yield:
+      return true;
+
+    case JSOp::Nop:
+    case JSOp::NopDestructuring:
+    case JSOp::TryDestructuring:
+    case JSOp::Lineno:
+    case JSOp::JumpTarget:
+    case JSOp::Undefined:
+    case JSOp::IfNe:
+    case JSOp::IfEq:
+    case JSOp::Return:
+    case JSOp::RetRval:
+    case JSOp::And:
+    case JSOp::Or:
+    case JSOp::Coalesce:
+    case JSOp::Try:
+    case JSOp::Throw:
+    case JSOp::Goto:
+    case JSOp::TableSwitch:
+    case JSOp::Case:
+    case JSOp::Default:
+    case JSOp::BitNot:
+    case JSOp::BitAnd:
+    case JSOp::BitOr:
+    case JSOp::BitXor:
+    case JSOp::Lsh:
+    case JSOp::Rsh:
+    case JSOp::Ursh:
+    case JSOp::Add:
+    case JSOp::Sub:
+    case JSOp::Mul:
+    case JSOp::Div:
+    case JSOp::Mod:
+    case JSOp::Pow:
+    case JSOp::Pos:
+    case JSOp::ToNumeric:
+    case JSOp::Neg:
+    case JSOp::Inc:
+    case JSOp::Dec:
+    case JSOp::ToString:
+    case JSOp::Eq:
+    case JSOp::Ne:
+    case JSOp::StrictEq:
+    case JSOp::StrictNe:
+    case JSOp::Lt:
+    case JSOp::Le:
+    case JSOp::Gt:
+    case JSOp::Ge:
+    case JSOp::Double:
+    case JSOp::BigInt:
+    case JSOp::String:
+    case JSOp::Symbol:
+    case JSOp::Zero:
+    case JSOp::One:
+    case JSOp::Null:
+    case JSOp::Void:
+    case JSOp::Hole:
+    case JSOp::False:
+    case JSOp::True:
+    case JSOp::Arguments:
+    case JSOp::Rest:
+    case JSOp::GetArg:
+    case JSOp::SetArg:
+    case JSOp::GetLocal:
+    case JSOp::SetLocal:
+    case JSOp::ThrowSetConst:
+    case JSOp::CheckLexical:
+    case JSOp::CheckAliasedLexical:
+    case JSOp::InitLexical:
+    case JSOp::Uninitialized:
+    case JSOp::Pop:
+    case JSOp::PopN:
+    case JSOp::DupAt:
+    case JSOp::NewArray:
+    case JSOp::NewInit:
+    case JSOp::NewObject:
+    case JSOp::InitElem:
+    case JSOp::InitHiddenElem:
+    case JSOp::InitLockedElem:
+    case JSOp::InitElemInc:
+    case JSOp::InitElemArray:
+    case JSOp::InitProp:
+    case JSOp::InitLockedProp:
+    case JSOp::InitHiddenProp:
+    case JSOp::InitPropGetter:
+    case JSOp::InitHiddenPropGetter:
+    case JSOp::InitPropSetter:
+    case JSOp::InitHiddenPropSetter:
+    case JSOp::InitElemGetter:
+    case JSOp::InitHiddenElemGetter:
+    case JSOp::InitElemSetter:
+    case JSOp::InitHiddenElemSetter:
+    case JSOp::FunCall:
+    case JSOp::FunApply:
+    case JSOp::SpreadCall:
+    case JSOp::Call:
+    case JSOp::CallIgnoresRv:
+    case JSOp::CallIter:
+    case JSOp::New:
+    case JSOp::Eval:
+    case JSOp::StrictEval:
+    case JSOp::Int8:
+    case JSOp::Uint16:
+    case JSOp::ResumeKind:
+    case JSOp::GetGName:
+    case JSOp::GetName:
+    case JSOp::GetIntrinsic:
+    case JSOp::GetImport:
+    case JSOp::BindGName:
+    case JSOp::BindName:
+    case JSOp::BindVar:
+    case JSOp::Dup:
+    case JSOp::Dup2:
+    case JSOp::Swap:
+    case JSOp::Pick:
+    case JSOp::Unpick:
+    case JSOp::GetAliasedVar:
+    case JSOp::Uint24:
+    case JSOp::ResumeIndex:
+    case JSOp::Int32:
+    case JSOp::LoopHead:
+    case JSOp::GetElem:
+    case JSOp::Not:
+    case JSOp::FunctionThis:
+    case JSOp::GlobalThis:
+    case JSOp::Callee:
+    case JSOp::EnvCallee:
+    case JSOp::SuperBase:
+    case JSOp::GetPropSuper:
+    case JSOp::GetElemSuper:
+    case JSOp::GetProp:
+    case JSOp::RegExp:
+    case JSOp::CallSiteObj:
+    case JSOp::Object:
+    case JSOp::ClassConstructor:
+    case JSOp::Typeof:
+    case JSOp::TypeofExpr:
+    case JSOp::ToAsyncIter:
+    case JSOp::ToPropertyKey:
+    case JSOp::Lambda:
+    case JSOp::LambdaArrow:
+    case JSOp::PushLexicalEnv:
+    case JSOp::PopLexicalEnv:
+    case JSOp::FreshenLexicalEnv:
+    case JSOp::RecreateLexicalEnv:
+    case JSOp::Iter:
+    case JSOp::MoreIter:
+    case JSOp::IsNoIter:
+    case JSOp::EndIter:
+    case JSOp::In:
+    case JSOp::HasOwn:
+    case JSOp::CheckPrivateField:
+    case JSOp::SetRval:
+    case JSOp::Instanceof:
+    case JSOp::DebugLeaveLexicalEnv:
+    case JSOp::Debugger:
+    case JSOp::GImplicitThis:
+    case JSOp::ImplicitThis:
+    case JSOp::NewTarget:
+    case JSOp::CheckIsObj:
+    case JSOp::CheckObjCoercible:
+    case JSOp::DebugCheckSelfHosted:
+    case JSOp::IsConstructing:
+    case JSOp::OptimizeSpreadCall:
+    case JSOp::ImportMeta:
+    case JSOp::InstrumentationActive:
+    case JSOp::InstrumentationCallback:
+    case JSOp::InstrumentationScriptId:
+    case JSOp::EnterWith:
+    case JSOp::LeaveWith:
+    case JSOp::SpreadNew:
+    case JSOp::SpreadEval:
+    case JSOp::StrictSpreadEval:
+    case JSOp::CheckClassHeritage:
+    case JSOp::FunWithProto:
+    case JSOp::ObjWithProto:
+    case JSOp::BuiltinObject:
+    case JSOp::DerivedConstructor:
+    case JSOp::CheckThis:
+    case JSOp::CheckReturn:
+    case JSOp::CheckThisReinit:
+    case JSOp::SuperFun:
+    case JSOp::SpreadSuperCall:
+    case JSOp::SuperCall:
+    case JSOp::PushVarEnv:
+    case JSOp::GetBoundName:
+    case JSOp::Exception:
+    case JSOp::IsGenClosing:
+    case JSOp::FinalYieldRval:
+    case JSOp::Resume:
+    case JSOp::CheckResumeKind:
+    case JSOp::AfterYield:
+    case JSOp::Await:
+    case JSOp::CanSkipAwait:
+    case JSOp::MaybeExtractAwaitValue:
+    case JSOp::Generator:
+    case JSOp::AsyncAwait:
+    case JSOp::AsyncResolve:
+    case JSOp::Finally:
+    case JSOp::GetRval:
+    case JSOp::Gosub:
+    case JSOp::Retsub:
+    case JSOp::ThrowMsg:
+    case JSOp::ForceInterpreter:
+      return false;
+  }
+
+  MOZ_ASSERT_UNREACHABLE("Invalid opcode");
+  return false;
+}
+
+bool DebuggerScript::CallData::getEffectfulOffsets() {
+  if (!ensureScript()) {
+    return false;
+  }
+
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+  for (BytecodeRange r(cx, script); !r.empty(); r.popFront()) {
+    if (BytecodeIsEffectful(r.frontOpcode())) {
+      if (!NewbornArrayPush(cx, result, NumberValue(r.frontOffset()))) {
+        return false;
+      }
+    }
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerScript::CallData::getAllOffsets() {
+  if (!ensureScript()) {
+    return false;
+  }
+
+  // First pass: determine which offsets in this script are jump targets and
+  // which line numbers jump to them.
+  FlowGraphSummary flowData(cx);
+  if (!flowData.populate(cx, script)) {
+    return false;
+  }
+
+  // Second pass: build the result array.
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+  for (BytecodeRangeWithPosition r(cx, script); !r.empty(); r.popFront()) {
+    if (!r.frontIsEntryPoint()) {
+      continue;
+    }
+
+    size_t offset = r.frontOffset();
+    size_t lineno = r.frontLineNumber();
+
+    // Make a note, if the current instruction is an entry point for the current
+    // line.
+    if (!flowData[offset].hasNoEdges() && flowData[offset].lineno() != lineno) {
+      // Get the offsets array for this line.
+      RootedObject offsets(cx);
+      RootedValue offsetsv(cx);
+
+      RootedId id(cx, INT_TO_JSID(lineno));
+
+      bool found;
+      if (!HasOwnProperty(cx, result, id, &found)) {
+        return false;
+      }
+      if (found && !GetProperty(cx, result, result, id, &offsetsv)) {
+        return false;
+      }
+
+      if (offsetsv.isObject()) {
+        offsets = &offsetsv.toObject();
+      } else {
+        MOZ_ASSERT(offsetsv.isUndefined());
+
+        // Create an empty offsets array for this line.
+        // Store it in the result array.
+        RootedId id(cx);
+        RootedValue v(cx, NumberValue(lineno));
+        offsets = NewDenseEmptyArray(cx);
+        if (!offsets || !PrimitiveValueToId<CanGC>(cx, v, &id)) {
+          return false;
+        }
+
+        RootedValue value(cx, ObjectValue(*offsets));
+        if (!DefineDataProperty(cx, result, id, value)) {
+          return false;
+        }
+      }
+
+      // Append the current offset to the offsets array.
+      if (!NewbornArrayPush(cx, offsets, NumberValue(offset))) {
+        return false;
+      }
+    }
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+class DebuggerScript::GetAllColumnOffsetsMatcher {
+  JSContext* cx_;
+  MutableHandleObject result_;
+
+  bool appendColumnOffsetEntry(size_t lineno, size_t column, size_t offset) {
+    RootedPlainObject entry(cx_, NewBuiltinClassInstance<PlainObject>(cx_));
+    if (!entry) {
+      return false;
+    }
+
+    RootedValue value(cx_, NumberValue(lineno));
+    if (!DefineDataProperty(cx_, entry, cx_->names().lineNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(column);
+    if (!DefineDataProperty(cx_, entry, cx_->names().columnNumber, value)) {
+      return false;
+    }
+
+    value = NumberValue(offset);
+    if (!DefineDataProperty(cx_, entry, cx_->names().offset, value)) {
+      return false;
+    }
+
+    return NewbornArrayPush(cx_, result_, ObjectValue(*entry));
+  }
+
+ public:
+  explicit GetAllColumnOffsetsMatcher(JSContext* cx, MutableHandleObject result)
+      : cx_(cx), result_(result) {}
+  using ReturnType = bool;
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    // First pass: determine which offsets in this script are jump targets
+    // and which positions jump to them.
+    FlowGraphSummary flowData(cx_);
+    if (!flowData.populate(cx_, script)) {
+      return false;
+    }
+
+    // Second pass: build the result array.
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    for (BytecodeRangeWithPosition r(cx_, script); !r.empty(); r.popFront()) {
+      size_t lineno = r.frontLineNumber();
+      size_t column = r.frontColumnNumber();
+      size_t offset = r.frontOffset();
+
+      // Make a note, if the current instruction is an entry point for
+      // the current position.
+      if (r.frontIsEntryPoint() && !flowData[offset].hasNoEdges() &&
+          (flowData[offset].lineno() != lineno ||
+           flowData[offset].column() != column)) {
+        if (!appendColumnOffsetEntry(lineno, column, offset)) {
+          return false;
+        }
+      }
+    }
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+
+    Vector<wasm::ExprLoc> offsets(cx_);
+    if (instance.debugEnabled() &&
+        !instance.debug().getAllColumnOffsets(&offsets)) {
+      return false;
+    }
+
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    for (uint32_t i = 0; i < offsets.length(); i++) {
+      size_t lineno = offsets[i].lineno;
+      size_t column = offsets[i].column;
+      size_t offset = offsets[i].offset;
+      if (!appendColumnOffsetEntry(lineno, column, offset)) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getAllColumnOffsets() {
+  RootedObject result(cx);
+  GetAllColumnOffsetsMatcher matcher(cx, &result);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+class DebuggerScript::GetLineOffsetsMatcher {
+  JSContext* cx_;
+  size_t lineno_;
+  MutableHandleObject result_;
+
+ public:
+  explicit GetLineOffsetsMatcher(JSContext* cx, size_t lineno,
+                                 MutableHandleObject result)
+      : cx_(cx), lineno_(lineno), result_(result) {}
+  using ReturnType = bool;
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    // First pass: determine which offsets in this script are jump targets and
+    // which line numbers jump to them.
+    FlowGraphSummary flowData(cx_);
+    if (!flowData.populate(cx_, script)) {
+      return false;
+    }
+
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    // Second pass: build the result array.
+    for (BytecodeRangeWithPosition r(cx_, script); !r.empty(); r.popFront()) {
+      if (!r.frontIsEntryPoint()) {
+        continue;
+      }
+
+      size_t offset = r.frontOffset();
+
+      // If the op at offset is an entry point, append offset to result.
+      if (r.frontLineNumber() == lineno_ && !flowData[offset].hasNoEdges() &&
+          flowData[offset].lineno() != lineno_) {
+        if (!NewbornArrayPush(cx_, result_, NumberValue(offset))) {
+          return false;
+        }
+      }
+    }
+
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+
+    Vector<uint32_t> offsets(cx_);
+    if (instance.debugEnabled() &&
+        !instance.debug().getLineOffsets(lineno_, &offsets)) {
+      return false;
+    }
+
+    result_.set(NewDenseEmptyArray(cx_));
+    if (!result_) {
+      return false;
+    }
+
+    for (uint32_t i = 0; i < offsets.length(); i++) {
+      if (!NewbornArrayPush(cx_, result_, NumberValue(offsets[i]))) {
+        return false;
+      }
+    }
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::getLineOffsets() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.getLineOffsets", 1)) {
+    return false;
+  }
+
+  // Parse lineno argument.
+  RootedValue linenoValue(cx, args[0]);
+  size_t lineno;
+  if (!ToNumber(cx, &linenoValue)) {
+    return false;
+  }
+  {
+    double d = linenoValue.toNumber();
+    lineno = size_t(d);
+    if (lineno != d) {
+      JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_LINE);
+      return false;
+    }
+  }
+
+  RootedObject result(cx);
+  GetLineOffsetsMatcher matcher(cx, lineno, &result);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+struct DebuggerScript::SetBreakpointMatcher {
+  JSContext* cx_;
+  Debugger* dbg_;
+  size_t offset_;
+  RootedObject handler_;
+  RootedObject debuggerObject_;
+
+  bool wrapCrossCompartmentEdges() {
+    if (!cx_->compartment()->wrap(cx_, &handler_) ||
+        !cx_->compartment()->wrap(cx_, &debuggerObject_)) {
+      return false;
+    }
+
+    // If the Debugger's compartment has killed incoming wrappers, we may not
+    // have gotten usable results from the 'wrap' calls. Treat it as a
+    // failure.
+    if (IsDeadProxyObject(handler_) || IsDeadProxyObject(debuggerObject_)) {
+      ReportAccessDenied(cx_);
+      return false;
+    }
+
+    return true;
+  }
+
+ public:
+  explicit SetBreakpointMatcher(JSContext* cx, Debugger* dbg, size_t offset,
+                                HandleObject handler)
+      : cx_(cx),
+        dbg_(dbg),
+        offset_(offset),
+        handler_(cx, handler),
+        debuggerObject_(cx_, dbg_->toJSObject()) {}
+
+  using ReturnType = bool;
+
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    if (!dbg_->observesScript(script)) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_NOT_DEBUGGING);
+      return false;
+    }
+
+    if (!EnsureScriptOffsetIsValid(cx_, script, offset_)) {
+      return false;
+    }
+
+    // Ensure observability *before* setting the breakpoint. If the script is
+    // not already a debuggee, trying to ensure observability after setting
+    // the breakpoint (and thus marking the script as a debuggee) will skip
+    // actually ensuring observability.
+    if (!dbg_->ensureExecutionObservabilityOfScript(cx_, script)) {
+      return false;
+    }
+
+    // A Breakpoint belongs logically to its script's compartment, so its
+    // references to its Debugger and handler must be properly wrapped.
+    AutoRealm ar(cx_, script);
+    if (!wrapCrossCompartmentEdges()) {
+      return false;
+    }
+
+    jsbytecode* pc = script->offsetToPC(offset_);
+    JSBreakpointSite* site =
+        DebugScript::getOrCreateBreakpointSite(cx_, script, pc);
+    if (!site) {
+      return false;
+    }
+
+    if (!cx_->zone()->new_<Breakpoint>(dbg_, debuggerObject_, site, handler_)) {
+      site->destroyIfEmpty(cx_->runtime()->defaultFreeOp());
+      return false;
+    }
+    AddCellMemory(script, sizeof(Breakpoint), MemoryUse::Breakpoint);
+
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    wasm::Instance& instance = wasmInstance->instance();
+    if (!instance.debugEnabled() ||
+        !instance.debug().hasBreakpointTrapAtOffset(offset_)) {
+      JS_ReportErrorNumberASCII(cx_, GetErrorMessage, nullptr,
+                                JSMSG_DEBUG_BAD_OFFSET);
+      return false;
+    }
+
+    // A Breakpoint belongs logically to its Instance's compartment, so its
+    // references to its Debugger and handler must be properly wrapped.
+    AutoRealm ar(cx_, wasmInstance);
+    if (!wrapCrossCompartmentEdges()) {
+      return false;
+    }
+
+    WasmBreakpointSite* site = instance.getOrCreateBreakpointSite(cx_, offset_);
+    if (!site) {
+      return false;
+    }
+
+    if (!cx_->zone()->new_<Breakpoint>(dbg_, debuggerObject_, site, handler_)) {
+      site->destroyIfEmpty(cx_->runtime()->defaultFreeOp());
+      return false;
+    }
+    AddCellMemory(wasmInstance, sizeof(Breakpoint), MemoryUse::Breakpoint);
+
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::setBreakpoint() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.setBreakpoint", 2)) {
+    return false;
+  }
+  Debugger* dbg = obj->owner();
+
+  size_t offset;
+  if (!ScriptOffset(cx, args[0], &offset)) {
+    return false;
+  }
+
+  RootedObject handler(cx, RequireObject(cx, args[1]));
+  if (!handler) {
+    return false;
+  }
+
+  SetBreakpointMatcher matcher(cx, dbg, offset, handler);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerScript::CallData::getBreakpoints() {
+  if (!ensureScript()) {
+    return false;
+  }
+  Debugger* dbg = obj->owner();
+
+  jsbytecode* pc;
+  if (args.length() > 0) {
+    size_t offset;
+    if (!ScriptOffset(cx, args[0], &offset) ||
+        !EnsureScriptOffsetIsValid(cx, script, offset)) {
+      return false;
+    }
+    pc = script->offsetToPC(offset);
+  } else {
+    pc = nullptr;
+  }
+
+  RootedObject arr(cx, NewDenseEmptyArray(cx));
+  if (!arr) {
+    return false;
+  }
+
+  for (unsigned i = 0; i < script->length(); i++) {
+    JSBreakpointSite* site =
+        DebugScript::getBreakpointSite(script, script->offsetToPC(i));
+    if (!site) {
+      continue;
+    }
+    if (!pc || site->pc == pc) {
+      for (Breakpoint* bp = site->firstBreakpoint(); bp;
+           bp = bp->nextInSite()) {
+        if (bp->debugger == dbg) {
+          RootedObject handler(cx, bp->getHandler());
+          if (!cx->compartment()->wrap(cx, &handler) ||
+              !NewbornArrayPush(cx, arr, ObjectValue(*handler))) {
+            return false;
+          }
+        }
+      }
+    }
+  }
+  args.rval().setObject(*arr);
+  return true;
+}
+
+class DebuggerScript::ClearBreakpointMatcher {
+  JSContext* cx_;
+  Debugger* dbg_;
+  RootedObject handler_;
+
+ public:
+  ClearBreakpointMatcher(JSContext* cx, Debugger* dbg, JSObject* handler)
+      : cx_(cx), dbg_(dbg), handler_(cx, handler) {}
+  using ReturnType = bool;
+
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    // A Breakpoint belongs logically to its script's compartment, so it holds
+    // its handler via a cross-compartment wrapper. But the handler passed to
+    // `clearBreakpoint` is same-compartment with the Debugger. Wrap it here,
+    // so that `DebugScript::clearBreakpointsIn` gets the right value to
+    // search for.
+    AutoRealm ar(cx_, script);
+    if (!cx_->compartment()->wrap(cx_, &handler_)) {
+      return false;
+    }
+
+    DebugScript::clearBreakpointsIn(cx_->runtime()->defaultFreeOp(), script,
+                                    dbg_, handler_);
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    if (!instance.debugEnabled()) {
+      return true;
+    }
+
+    // A Breakpoint belongs logically to its instance's compartment, so it
+    // holds its handler via a cross-compartment wrapper. But the handler
+    // passed to `clearBreakpoint` is same-compartment with the Debugger. Wrap
+    // it here, so that `DebugState::clearBreakpointsIn` gets the right value
+    // to search for.
+    AutoRealm ar(cx_, instanceObj);
+    if (!cx_->compartment()->wrap(cx_, &handler_)) {
+      return false;
+    }
+
+    instance.debug().clearBreakpointsIn(cx_->runtime()->defaultFreeOp(),
+                                        instanceObj, dbg_, handler_);
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::clearBreakpoint() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.clearBreakpoint", 1)) {
+    return false;
+  }
+  Debugger* dbg = obj->owner();
+
+  JSObject* handler = RequireObject(cx, args[0]);
+  if (!handler) {
+    return false;
+  }
+
+  ClearBreakpointMatcher matcher(cx, dbg, handler);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+bool DebuggerScript::CallData::clearAllBreakpoints() {
+  Debugger* dbg = obj->owner();
+  ClearBreakpointMatcher matcher(cx, dbg, nullptr);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+  args.rval().setUndefined();
+  return true;
+}
+
+class DebuggerScript::IsInCatchScopeMatcher {
+  JSContext* cx_;
+  size_t offset_;
+  bool isInCatch_;
+
+ public:
+  explicit IsInCatchScopeMatcher(JSContext* cx, size_t offset)
+      : cx_(cx), offset_(offset), isInCatch_(false) {}
+  using ReturnType = bool;
+
+  inline bool isInCatch() const { return isInCatch_; }
+
+  ReturnType match(Handle<BaseScript*> base) {
+    RootedScript script(cx_, DelazifyScript(cx_, base));
+    if (!script) {
+      return false;
+    }
+
+    if (!EnsureScriptOffsetIsValid(cx_, script, offset_)) {
+      return false;
+    }
+
+    for (const TryNote& tn : script->trynotes()) {
+      if (tn.start <= offset_ && offset_ < tn.start + tn.length &&
+          tn.kind() == TryNoteKind::Catch) {
+        isInCatch_ = true;
+        return true;
+      }
+    }
+
+    isInCatch_ = false;
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instance) {
+    isInCatch_ = false;
+    return true;
+  }
+};
+
+bool DebuggerScript::CallData::isInCatchScope() {
+  if (!args.requireAtLeast(cx, "Debugger.Script.isInCatchScope", 1)) {
+    return false;
+  }
+
+  size_t offset;
+  if (!ScriptOffset(cx, args[0], &offset)) {
+    return false;
+  }
+
+  IsInCatchScopeMatcher matcher(cx, offset);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+  args.rval().setBoolean(matcher.isInCatch());
+  return true;
+}
+
+bool DebuggerScript::CallData::getOffsetsCoverage() {
+  if (!ensureScript()) {
+    return false;
+  }
+
+  // If the script has no coverage information, then skip this and return null
+  // instead.
+  if (!script->hasScriptCounts()) {
+    args.rval().setNull();
+    return true;
+  }
+
+  ScriptCounts* sc = &script->getScriptCounts();
+
+  // If the main ever got visited, then assume that any code before main got
+  // visited once.
+  uint64_t hits = 0;
+  const PCCounts* counts =
+      sc->maybeGetPCCounts(script->pcToOffset(script->main()));
+  if (counts->numExec()) {
+    hits = 1;
+  }
+
+  // Build an array of objects which are composed of 4 properties:
+  //  - offset          PC offset of the current opcode.
+  //  - lineNumber      Line of the current opcode.
+  //  - columnNumber    Column of the current opcode.
+  //  - count           Number of times the instruction got executed.
+  RootedObject result(cx, NewDenseEmptyArray(cx));
+  if (!result) {
+    return false;
+  }
+
+  RootedId offsetId(cx, NameToId(cx->names().offset));
+  RootedId lineNumberId(cx, NameToId(cx->names().lineNumber));
+  RootedId columnNumberId(cx, NameToId(cx->names().columnNumber));
+  RootedId countId(cx, NameToId(cx->names().count));
+
+  RootedObject item(cx);
+  RootedValue offsetValue(cx);
+  RootedValue lineNumberValue(cx);
+  RootedValue columnNumberValue(cx);
+  RootedValue countValue(cx);
+
+  // Iterate linearly over the bytecode.
+  for (BytecodeRangeWithPosition r(cx, script); !r.empty(); r.popFront()) {
+    size_t offset = r.frontOffset();
+
+    // The beginning of each non-branching sequences of instruction set the
+    // number of execution of the current instruction and any following
+    // instruction.
+    counts = sc->maybeGetPCCounts(offset);
+    if (counts) {
+      hits = counts->numExec();
+    }
+
+    offsetValue.setNumber(double(offset));
+    lineNumberValue.setNumber(double(r.frontLineNumber()));
+    columnNumberValue.setNumber(double(r.frontColumnNumber()));
+    countValue.setNumber(double(hits));
+
+    // Create a new object with the offset, line number, column number, the
+    // number of hit counts, and append it to the array.
+    item = NewObjectWithGivenProto<PlainObject>(cx, nullptr);
+    if (!item || !DefineDataProperty(cx, item, offsetId, offsetValue) ||
+        !DefineDataProperty(cx, item, lineNumberId, lineNumberValue) ||
+        !DefineDataProperty(cx, item, columnNumberId, columnNumberValue) ||
+        !DefineDataProperty(cx, item, countId, countValue) ||
+        !NewbornArrayPush(cx, result, ObjectValue(*item))) {
+      return false;
+    }
+
+    // If the current instruction has thrown, then decrement the hit counts
+    // with the number of throws.
+    counts = sc->maybeGetThrowCounts(offset);
+    if (counts) {
+      hits -= counts->numExec();
+    }
+  }
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+bool DebuggerScript::CallData::setInstrumentationId() {
+  if (!ensureScriptMaybeLazy()) {
+    return false;
+  }
+
+  if (!obj->getInstrumentationId().isUndefined()) {
+    JS_ReportErrorASCII(cx, "Script instrumentation ID is already set");
+    return false;
+  }
+
+  if (!args.get(0).isNumber()) {
+    JS_ReportErrorASCII(cx, "Script instrumentation ID must be a number");
+    return false;
+  }
+
+  obj->setReservedSlot(INSTRUMENTATION_ID_SLOT, args.get(0));
+
+  args.rval().setUndefined();
+  return true;
+}
+
+/* static */
+bool DebuggerScript::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Script");
+  return false;
+}
+
+const JSPropertySpec DebuggerScript::properties_[] = {
+    JS_DEBUG_PSG("isGeneratorFunction", getIsGeneratorFunction),
+    JS_DEBUG_PSG("isAsyncFunction", getIsAsyncFunction),
+    JS_DEBUG_PSG("isFunction", getIsFunction),
+    JS_DEBUG_PSG("isModule", getIsModule),
+    JS_DEBUG_PSG("displayName", getDisplayName),
+    JS_DEBUG_PSG("parameterNames", getParameterNames),
+    JS_DEBUG_PSG("url", getUrl),
+    JS_DEBUG_PSG("startLine", getStartLine),
+    JS_DEBUG_PSG("startColumn", getStartColumn),
+    JS_DEBUG_PSG("lineCount", getLineCount),
+    JS_DEBUG_PSG("source", getSource),
+    JS_DEBUG_PSG("sourceStart", getSourceStart),
+    JS_DEBUG_PSG("sourceLength", getSourceLength),
+    JS_DEBUG_PSG("mainOffset", getMainOffset),
+    JS_DEBUG_PSG("global", getGlobal),
+    JS_DEBUG_PSG("format", getFormat),
+    JS_PS_END};
+
+const JSFunctionSpec DebuggerScript::methods_[] = {
+    JS_DEBUG_FN("getChildScripts", getChildScripts, 0),
+    JS_DEBUG_FN("getPossibleBreakpoints", getPossibleBreakpoints, 0),
+    JS_DEBUG_FN("getPossibleBreakpointOffsets", getPossibleBreakpointOffsets,
+                0),
+    JS_DEBUG_FN("setBreakpoint", setBreakpoint, 2),
+    JS_DEBUG_FN("getBreakpoints", getBreakpoints, 1),
+    JS_DEBUG_FN("clearBreakpoint", clearBreakpoint, 1),
+    JS_DEBUG_FN("clearAllBreakpoints", clearAllBreakpoints, 0),
+    JS_DEBUG_FN("isInCatchScope", isInCatchScope, 1),
+    JS_DEBUG_FN("getOffsetMetadata", getOffsetMetadata, 1),
+    JS_DEBUG_FN("getOffsetsCoverage", getOffsetsCoverage, 0),
+    JS_DEBUG_FN("getEffectfulOffsets", getEffectfulOffsets, 1),
+    JS_DEBUG_FN("setInstrumentationId", setInstrumentationId, 1),
+
+    // The following APIs are deprecated due to their reliance on the
+    // under-defined 'entrypoint' concept. Make use of getPossibleBreakpoints,
+    // getPossibleBreakpointOffsets, or getOffsetMetadata instead.
+    JS_DEBUG_FN("getAllOffsets", getAllOffsets, 0),
+    JS_DEBUG_FN("getAllColumnOffsets", getAllColumnOffsets, 0),
+    JS_DEBUG_FN("getLineOffsets", getLineOffsets, 1),
+    JS_DEBUG_FN("getOffsetLocation", getOffsetLocation, 0), JS_FS_END};
diff --git a/js/src/debugger/Script.h b/js/src/debugger/Script.h
new file mode 100644
index 0000000000..6478c0d131
--- /dev/null
+++ b/js/src/debugger/Script.h
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef debugger_Script_h
+#define debugger_Script_h
+
+#include "jsapi.h"  // for Handle, JSFunctionSpec, JSPropertySpec
+
+#include "jstypes.h"            // for JS_PUBLIC_API
+#include "NamespaceImports.h"   // for Value, HandleObject, CallArgs
+#include "debugger/Debugger.h"  // for DebuggerScriptReferent
+#include "gc/Rooting.h"         // for HandleNativeObject
+#include "vm/NativeObject.h"    // for NativeObject
+
+class JS_PUBLIC_API JSObject;
+
+namespace js {
+
+class BaseScript;
+class GlobalObject;
+
+namespace gc {
+struct Cell;
+}
+
+class DebuggerScript : public NativeObject {
+ public:
+  static const JSClass class_;
+
+  enum {
+    OWNER_SLOT,
+
+    // Holds any instrumentation ID that has been assigned to the script.
+    INSTRUMENTATION_ID_SLOT,
+
+    RESERVED_SLOTS,
+  };
+
+  static NativeObject* initClass(JSContext* cx, Handle<GlobalObject*> global,
+                                 HandleObject debugCtor);
+  static DebuggerScript* create(JSContext* cx, HandleObject proto,
+                                Handle<DebuggerScriptReferent> referent,
+                                HandleNativeObject debugger);
+
+  void trace(JSTracer* trc);
+
+  using ReferentVariant = DebuggerScriptReferent;
+
+  inline gc::Cell* getReferentCell() const;
+  inline js::BaseScript* getReferentScript() const;
+  inline DebuggerScriptReferent getReferent() const;
+
+  static DebuggerScript* check(JSContext* cx, HandleValue v);
+
+  static bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+
+  Value getInstrumentationId() const {
+    return getSlot(INSTRUMENTATION_ID_SLOT);
+  }
+
+  bool isInstance() const;
+  Debugger* owner() const;
+
+ private:
+  static const JSClassOps classOps_;
+
+  static const JSPropertySpec properties_[];
+  static const JSFunctionSpec methods_[];
+
+  struct GetLineCountMatcher;
+  class GetSourceMatcher;
+  template <bool OnlyOffsets>
+  class GetPossibleBreakpointsMatcher;
+  class GetOffsetMetadataMatcher;
+  class GetOffsetLocationMatcher;
+  class GetAllColumnOffsetsMatcher;
+  class GetLineOffsetsMatcher;
+  struct SetBreakpointMatcher;
+  class ClearBreakpointMatcher;
+  class IsInCatchScopeMatcher;
+};
+
+} /* namespace js */
+
+#endif /* debugger_Script_h */
diff --git a/js/src/debugger/Source.cpp b/js/src/debugger/Source.cpp
new file mode 100644
index 0000000000..3d0f563cc7
--- /dev/null
+++ b/js/src/debugger/Source.cpp
@@ -0,0 +1,689 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "debugger/Source.h"
+
+#include "mozilla/Assertions.h"  // for AssertionConditionType, MOZ_ASSERT
+#include "mozilla/Maybe.h"       // for Some, Maybe, Nothing
+#include "mozilla/Variant.h"     // for AsVariant, Variant
+
+#include <stdint.h>  // for uint32_t
+#include <string.h>  // for memcpy
+#include <utility>   // for move
+
+#include "jsapi.h"  // for JS_ReportErrorNumberASCII, JS_CopyStringCharsZ
+
+#include "debugger/Debugger.h"  // for DebuggerSourceReferent, Debugger
+#include "debugger/Script.h"    // for DebuggerScript
+#include "gc/Tracer.h"  // for TraceManuallyBarrieredCrossCompartmentEdge
+#include "js/CompilationAndEvaluation.h"  // for Compile
+#include "js/experimental/TypedData.h"    // for JS_NewUint8Array
+#include "js/friend/ErrorMessages.h"      // for GetErrorMessage, JSMSG_*
+#include "js/SourceText.h"                // for JS::SourceOwnership
+#include "vm/BytecodeUtil.h"              // for JSDVG_SEARCH_STACK
+#include "vm/JSContext.h"                 // for JSContext (ptr only)
+#include "vm/JSObject.h"                  // for JSObject, RequireObject
+#include "vm/JSScript.h"          // for ScriptSource, ScriptSourceObject
+#include "vm/ObjectGroup.h"       // for TenuredObject
+#include "vm/StringType.h"        // for NewStringCopyZ, JSString (ptr only)
+#include "vm/TypedArrayObject.h"  // for TypedArrayObject, JSObject::is
+#include "wasm/WasmCode.h"        // for Metadata
+#include "wasm/WasmDebug.h"       // for DebugState
+#include "wasm/WasmInstance.h"    // for Instance
+#include "wasm/WasmJS.h"          // for WasmInstanceObject
+#include "wasm/WasmTypes.h"       // for Bytes, RootedWasmInstanceObject
+
+#include "debugger/Debugger-inl.h"  // for Debugger::fromJSObject
+#include "vm/JSObject-inl.h"        // for InitClass
+#include "vm/NativeObject-inl.h"    // for NewTenuredObjectWithGivenProto
+
+namespace js {
+class GlobalObject;
+}
+
+using namespace js;
+
+using mozilla::AsVariant;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::Some;
+
+const JSClassOps DebuggerSource::classOps_ = {
+    nullptr,                          // addProperty
+    nullptr,                          // delProperty
+    nullptr,                          // enumerate
+    nullptr,                          // newEnumerate
+    nullptr,                          // resolve
+    nullptr,                          // mayResolve
+    nullptr,                          // finalize
+    nullptr,                          // call
+    nullptr,                          // hasInstance
+    nullptr,                          // construct
+    CallTraceMethod<DebuggerSource>,  // trace
+};
+
+const JSClass DebuggerSource::class_ = {
+    "Source", JSCLASS_HAS_PRIVATE | JSCLASS_HAS_RESERVED_SLOTS(RESERVED_SLOTS),
+    &classOps_};
+
+/* static */
+NativeObject* DebuggerSource::initClass(JSContext* cx,
+                                        Handle<GlobalObject*> global,
+                                        HandleObject debugCtor) {
+  return InitClass(cx, debugCtor, nullptr, &class_, construct, 0, properties_,
+                   methods_, nullptr, nullptr);
+}
+
+/* static */
+DebuggerSource* DebuggerSource::create(JSContext* cx, HandleObject proto,
+                                       Handle<DebuggerSourceReferent> referent,
+                                       HandleNativeObject debugger) {
+  Rooted<DebuggerSource*> sourceObj(
+      cx, NewTenuredObjectWithGivenProto<DebuggerSource>(cx, proto));
+  if (!sourceObj) {
+    return nullptr;
+  }
+  sourceObj->setReservedSlot(OWNER_SLOT, ObjectValue(*debugger));
+  referent.get().match(
+      [&](auto sourceHandle) { sourceObj->setPrivateGCThing(sourceHandle); });
+
+  return sourceObj;
+}
+
+Debugger* DebuggerSource::owner() const {
+  MOZ_ASSERT(isInstance());
+  JSObject* dbgobj = &getReservedSlot(OWNER_SLOT).toObject();
+  return Debugger::fromJSObject(dbgobj);
+}
+
+// For internal use only.
+NativeObject* DebuggerSource::getReferentRawObject() const {
+  return static_cast<NativeObject*>(getPrivate());
+}
+
+DebuggerSourceReferent DebuggerSource::getReferent() const {
+  if (NativeObject* referent = getReferentRawObject()) {
+    if (referent->is<ScriptSourceObject>()) {
+      return AsVariant(&referent->as<ScriptSourceObject>());
+    }
+    return AsVariant(&referent->as<WasmInstanceObject>());
+  }
+  return AsVariant(static_cast<ScriptSourceObject*>(nullptr));
+}
+
+void DebuggerSource::trace(JSTracer* trc) {
+  // There is a barrier on private pointers, so the Unbarriered marking
+  // is okay.
+  if (JSObject* referent = getReferentRawObject()) {
+    TraceManuallyBarrieredCrossCompartmentEdge(
+        trc, static_cast<JSObject*>(this), &referent,
+        "Debugger.Source referent");
+    setPrivateUnbarriered(referent);
+  }
+}
+
+/* static */
+bool DebuggerSource::construct(JSContext* cx, unsigned argc, Value* vp) {
+  JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_NO_CONSTRUCTOR,
+                            "Debugger.Source");
+  return false;
+}
+
+/* static */
+DebuggerSource* DebuggerSource::check(JSContext* cx, HandleValue thisv) {
+  JSObject* thisobj = RequireObject(cx, thisv);
+  if (!thisobj) {
+    return nullptr;
+  }
+  if (!thisobj->is<DebuggerSource>()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Source",
+                              "method", thisobj->getClass()->name);
+    return nullptr;
+  }
+
+  DebuggerSource* thisSourceObj = &thisobj->as<DebuggerSource>();
+
+  if (!thisSourceObj->isInstance()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_INCOMPATIBLE_PROTO, "Debugger.Source",
+                              "method", "prototype object");
+    return nullptr;
+  }
+
+  return thisSourceObj;
+}
+
+struct MOZ_STACK_CLASS DebuggerSource::CallData {
+  JSContext* cx;
+  const CallArgs& args;
+
+  HandleDebuggerSource obj;
+  Rooted<DebuggerSourceReferent> referent;
+
+  CallData(JSContext* cx, const CallArgs& args, HandleDebuggerSource obj)
+      : cx(cx), args(args), obj(obj), referent(cx, obj->getReferent()) {}
+
+  bool getText();
+  bool getBinary();
+  bool getURL();
+  bool getStartLine();
+  bool getId();
+  bool getDisplayURL();
+  bool getElement();
+  bool getElementProperty();
+  bool getIntroductionScript();
+  bool getIntroductionOffset();
+  bool getIntroductionType();
+  bool setSourceMapURL();
+  bool getSourceMapURL();
+  bool reparse();
+
+  using Method = bool (CallData::*)();
+
+  template <Method MyMethod>
+  static bool ToNative(JSContext* cx, unsigned argc, Value* vp);
+};
+
+template <DebuggerSource::CallData::Method MyMethod>
+/* static */
+bool DebuggerSource::CallData::ToNative(JSContext* cx, unsigned argc,
+                                        Value* vp) {
+  CallArgs args = CallArgsFromVp(argc, vp);
+
+  RootedDebuggerSource obj(cx, DebuggerSource::check(cx, args.thisv()));
+  if (!obj) {
+    return false;
+  }
+
+  CallData data(cx, args, obj);
+  return (data.*MyMethod)();
+}
+
+class DebuggerSourceGetTextMatcher {
+  JSContext* cx_;
+
+ public:
+  explicit DebuggerSourceGetTextMatcher(JSContext* cx) : cx_(cx) {}
+
+  using ReturnType = JSString*;
+
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    bool hasSourceText;
+    if (!ScriptSource::loadSource(cx_, ss, &hasSourceText)) {
+      return nullptr;
+    }
+    if (!hasSourceText) {
+      return NewStringCopyZ<CanGC>(cx_, "[no source]");
+    }
+
+    if (ss->isFunctionBody()) {
+      return ss->functionBodyString(cx_);
+    }
+
+    return ss->substring(cx_, 0, ss->length());
+  }
+
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    const char* msg;
+    if (!instance.debugEnabled()) {
+      msg = "Restart with developer tools open to view WebAssembly source.";
+    } else {
+      msg = "[debugger missing wasm binary-to-text conversion]";
+    }
+    return NewStringCopyZ<CanGC>(cx_, msg);
+  }
+};
+
+bool DebuggerSource::CallData::getText() {
+  Value textv = obj->getReservedSlot(TEXT_SLOT);
+  if (!textv.isUndefined()) {
+    MOZ_ASSERT(textv.isString());
+    args.rval().set(textv);
+    return true;
+  }
+
+  DebuggerSourceGetTextMatcher matcher(cx);
+  JSString* str = referent.match(matcher);
+  if (!str) {
+    return false;
+  }
+
+  args.rval().setString(str);
+  obj->setReservedSlot(TEXT_SLOT, args.rval());
+  return true;
+}
+
+bool DebuggerSource::CallData::getBinary() {
+  if (!referent.is<WasmInstanceObject*>()) {
+    ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK,
+                     args.thisv(), nullptr, "a wasm source");
+    return false;
+  }
+
+  RootedWasmInstanceObject instanceObj(cx, referent.as<WasmInstanceObject*>());
+  wasm::Instance& instance = instanceObj->instance();
+
+  if (!instance.debugEnabled()) {
+    JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                              JSMSG_DEBUG_NO_BINARY_SOURCE);
+    return false;
+  }
+
+  const wasm::Bytes& bytecode = instance.debug().bytecode();
+  RootedObject arr(cx, JS_NewUint8Array(cx, bytecode.length()));
+  if (!arr) {
+    return false;
+  }
+
+  memcpy(arr->as<TypedArrayObject>().dataPointerUnshared(), bytecode.begin(),
+         bytecode.length());
+
+  args.rval().setObject(*arr);
+  return true;
+}
+
+class DebuggerSourceGetURLMatcher {
+  JSContext* cx_;
+
+ public:
+  explicit DebuggerSourceGetURLMatcher(JSContext* cx) : cx_(cx) {}
+
+  using ReturnType = Maybe<JSString*>;
+
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    MOZ_ASSERT(ss);
+    if (ss->filename()) {
+      JSString* str = NewStringCopyZ<CanGC>(cx_, ss->filename());
+      return Some(str);
+    }
+    return Nothing();
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    return Some(instanceObj->instance().createDisplayURL(cx_));
+  }
+};
+
+bool DebuggerSource::CallData::getURL() {
+  DebuggerSourceGetURLMatcher matcher(cx);
+  Maybe<JSString*> str = referent.match(matcher);
+  if (str.isSome()) {
+    if (!*str) {
+      return false;
+    }
+    args.rval().setString(*str);
+  } else {
+    args.rval().setNull();
+  }
+  return true;
+}
+
+class DebuggerSourceGetStartLineMatcher {
+ public:
+  using ReturnType = uint32_t;
+
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    return ss->startLine();
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) { return 0; }
+};
+
+bool DebuggerSource::CallData::getStartLine() {
+  DebuggerSourceGetStartLineMatcher matcher;
+  uint32_t line = referent.match(matcher);
+  args.rval().setNumber(line);
+  return true;
+}
+
+class DebuggerSourceGetIdMatcher {
+ public:
+  using ReturnType = uint32_t;
+
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    return ss->id();
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) { return 0; }
+};
+
+bool DebuggerSource::CallData::getId() {
+  DebuggerSourceGetIdMatcher matcher;
+  uint32_t id = referent.match(matcher);
+  args.rval().setNumber(id);
+  return true;
+}
+
+struct DebuggerSourceGetDisplayURLMatcher {
+  using ReturnType = const char16_t*;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    MOZ_ASSERT(ss);
+    return ss->hasDisplayURL() ? ss->displayURL() : nullptr;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    return wasmInstance->instance().metadata().displayURL();
+  }
+};
+
+bool DebuggerSource::CallData::getDisplayURL() {
+  DebuggerSourceGetDisplayURLMatcher matcher;
+  if (const char16_t* displayURL = referent.match(matcher)) {
+    JSString* str = JS_NewUCStringCopyZ(cx, displayURL);
+    if (!str) {
+      return false;
+    }
+    args.rval().setString(str);
+  } else {
+    args.rval().setNull();
+  }
+  return true;
+}
+
+struct DebuggerSourceGetElementMatcher {
+  JSContext* mCx = nullptr;
+  explicit DebuggerSourceGetElementMatcher(JSContext* cx_) : mCx(cx_) {}
+  using ReturnType = JSObject*;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    return sourceObject->unwrappedElement(mCx);
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) { return nullptr; }
+};
+
+bool DebuggerSource::CallData::getElement() {
+  DebuggerSourceGetElementMatcher matcher(cx);
+  if (JSObject* element = referent.match(matcher)) {
+    args.rval().setObjectOrNull(element);
+    if (!obj->owner()->wrapDebuggeeValue(cx, args.rval())) {
+      return false;
+    }
+  } else {
+    args.rval().setUndefined();
+  }
+  return true;
+}
+
+struct DebuggerSourceGetElementPropertyMatcher {
+  using ReturnType = Value;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    return sourceObject->unwrappedElementAttributeName();
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    return UndefinedValue();
+  }
+};
+
+bool DebuggerSource::CallData::getElementProperty() {
+  DebuggerSourceGetElementPropertyMatcher matcher;
+  args.rval().set(referent.match(matcher));
+  return obj->owner()->wrapDebuggeeValue(cx, args.rval());
+}
+
+class DebuggerSourceGetIntroductionScriptMatcher {
+  JSContext* cx_;
+  Debugger* dbg_;
+  MutableHandleValue rval_;
+
+ public:
+  DebuggerSourceGetIntroductionScriptMatcher(JSContext* cx, Debugger* dbg,
+                                             MutableHandleValue rval)
+      : cx_(cx), dbg_(dbg), rval_(rval) {}
+
+  using ReturnType = bool;
+
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    Rooted<BaseScript*> script(cx_,
+                               sourceObject->unwrappedIntroductionScript());
+    if (script) {
+      RootedObject scriptDO(cx_, dbg_->wrapScript(cx_, script));
+      if (!scriptDO) {
+        return false;
+      }
+      rval_.setObject(*scriptDO);
+    } else {
+      rval_.setUndefined();
+    }
+    return true;
+  }
+
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    RootedObject ds(cx_, dbg_->wrapWasmScript(cx_, wasmInstance));
+    if (!ds) {
+      return false;
+    }
+    rval_.setObject(*ds);
+    return true;
+  }
+};
+
+bool DebuggerSource::CallData::getIntroductionScript() {
+  Debugger* dbg = obj->owner();
+  DebuggerSourceGetIntroductionScriptMatcher matcher(cx, dbg, args.rval());
+  return referent.match(matcher);
+}
+
+struct DebuggerGetIntroductionOffsetMatcher {
+  using ReturnType = Value;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    // Regardless of what's recorded in the ScriptSourceObject and
+    // ScriptSource, only hand out the introduction offset if we also have
+    // the script within which it applies.
+    ScriptSource* ss = sourceObject->source();
+    if (ss->hasIntroductionOffset() &&
+        sourceObject->unwrappedIntroductionScript()) {
+      return Int32Value(ss->introductionOffset());
+    }
+    return UndefinedValue();
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) {
+    return UndefinedValue();
+  }
+};
+
+bool DebuggerSource::CallData::getIntroductionOffset() {
+  DebuggerGetIntroductionOffsetMatcher matcher;
+  args.rval().set(referent.match(matcher));
+  return true;
+}
+
+struct DebuggerSourceGetIntroductionTypeMatcher {
+  using ReturnType = const char*;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    MOZ_ASSERT(ss);
+    return ss->hasIntroductionType() ? ss->introductionType() : nullptr;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> wasmInstance) { return "wasm"; }
+};
+
+bool DebuggerSource::CallData::getIntroductionType() {
+  DebuggerSourceGetIntroductionTypeMatcher matcher;
+  if (const char* introductionType = referent.match(matcher)) {
+    JSString* str = NewStringCopyZ<CanGC>(cx, introductionType);
+    if (!str) {
+      return false;
+    }
+    args.rval().setString(str);
+  } else {
+    args.rval().setUndefined();
+  }
+
+  return true;
+}
+
+ScriptSourceObject* EnsureSourceObject(JSContext* cx,
+                                       HandleDebuggerSource obj) {
+  if (!obj->getReferent().is<ScriptSourceObject*>()) {
+    RootedValue v(cx, ObjectValue(*obj));
+    ReportValueError(cx, JSMSG_DEBUG_BAD_REFERENT, JSDVG_SEARCH_STACK, v,
+                     nullptr, "a JS source");
+    return nullptr;
+  }
+  return obj->getReferent().as<ScriptSourceObject*>();
+}
+
+bool DebuggerSource::CallData::setSourceMapURL() {
+  RootedScriptSourceObject sourceObject(cx, EnsureSourceObject(cx, obj));
+  if (!sourceObject) {
+    return false;
+  }
+  ScriptSource* ss = sourceObject->source();
+  MOZ_ASSERT(ss);
+
+  if (!args.requireAtLeast(cx, "set sourceMapURL", 1)) {
+    return false;
+  }
+
+  JSString* str = ToString<CanGC>(cx, args[0]);
+  if (!str) {
+    return false;
+  }
+
+  UniqueTwoByteChars chars = JS_CopyStringCharsZ(cx, str);
+  if (!chars) {
+    return false;
+  }
+
+  if (!ss->setSourceMapURL(cx, std::move(chars))) {
+    return false;
+  }
+
+  args.rval().setUndefined();
+  return true;
+}
+
+class DebuggerSourceGetSourceMapURLMatcher {
+  JSContext* cx_;
+  MutableHandleString result_;
+
+ public:
+  explicit DebuggerSourceGetSourceMapURLMatcher(JSContext* cx,
+                                                MutableHandleString result)
+      : cx_(cx), result_(result) {}
+
+  using ReturnType = bool;
+  ReturnType match(HandleScriptSourceObject sourceObject) {
+    ScriptSource* ss = sourceObject->source();
+    MOZ_ASSERT(ss);
+    if (!ss->hasSourceMapURL()) {
+      result_.set(nullptr);
+      return true;
+    }
+    JSString* str = JS_NewUCStringCopyZ(cx_, ss->sourceMapURL());
+    if (!str) {
+      return false;
+    }
+    result_.set(str);
+    return true;
+  }
+  ReturnType match(Handle<WasmInstanceObject*> instanceObj) {
+    wasm::Instance& instance = instanceObj->instance();
+    if (!instance.debugEnabled()) {
+      result_.set(nullptr);
+      return true;
+    }
+
+    RootedString str(cx_);
+    if (!instance.debug().getSourceMappingURL(cx_, &str)) {
+      return false;
+    }
+
+    result_.set(str);
+    return true;
+  }
+};
+
+bool DebuggerSource::CallData::getSourceMapURL() {
+  RootedString result(cx);
+  DebuggerSourceGetSourceMapURLMatcher matcher(cx, &result);
+  if (!referent.match(matcher)) {
+    return false;
+  }
+  if (result) {
+    args.rval().setString(result);
+  } else {
+    args.rval().setNull();
+  }
+  return true;
+}
+
+template <typename Unit>
+static JSScript* ReparseSource(JSContext* cx, HandleScriptSourceObject sso) {
+  AutoRealm ar(cx, sso);
+  ScriptSource* ss = sso->source();
+
+  JS::CompileOptions options(cx);
+  options.hideScriptFromDebugger = true;
+  options.setFileAndLine(ss->filename(), ss->startLine());
+
+  UncompressedSourceCache::AutoHoldEntry holder;
+
+  ScriptSource::PinnedUnits<Unit> units(cx, ss, holder, 0, ss->length());
+  if (!units.get()) {
+    return nullptr;
+  }
+
+  JS::SourceText<Unit> srcBuf;
+  if (!srcBuf.init(cx, units.get(), ss->length(),
+                   JS::SourceOwnership::Borrowed)) {
+    return nullptr;
+  }
+
+  return JS::Compile(cx, options, srcBuf);
+}
+
+bool DebuggerSource::CallData::reparse() {
+  RootedScriptSourceObject sourceObject(cx, EnsureSourceObject(cx, obj));
+  if (!sourceObject) {
+    return false;
+  }
+
+  if (!sourceObject->source()->hasSourceText()) {
+    JS_ReportErrorASCII(cx, "Source object missing text");
+    return false;
+  }
+
+  RootedScript script(cx);
+  if (sourceObject->source()->hasSourceType<mozilla::Utf8Unit>()) {
+    script = ReparseSource<mozilla::Utf8Unit>(cx, sourceObject);
+  } else {
+    script = ReparseSource<char16_t>(cx, sourceObject);
+  }
+
+  if (!script) {
+    return false;
+  }
+
+  Debugger* dbg = obj->owner();
+  RootedObject scriptDO(cx, dbg->wrapScript(cx, script));
+  if (!scriptDO) {
+    return false;
+  }
+
+  args.rval().setObject(*scriptDO);
+  return true;
+}
+
+const JSPropertySpec DebuggerSource::properties_[] = {
+    JS_DEBUG_PSG("text", getText),
+    JS_DEBUG_PSG("binary", getBinary),
+    JS_DEBUG_PSG("url", getURL),
+    JS_DEBUG_PSG("startLine", getStartLine),
+    JS_DEBUG_PSG("id", getId),
+    JS_DEBUG_PSG("element", getElement),
+    JS_DEBUG_PSG("displayURL", getDisplayURL),
+    JS_DEBUG_PSG("introductionScript", getIntroductionScript),
+    JS_DEBUG_PSG("introductionOffset", getIntroductionOffset),
+    JS_DEBUG_PSG("introductionType", getIntroductionType),
+    JS_DEBUG_PSG("elementAttributeName", getElementProperty),
+    JS_DEBUG_PSGS("sourceMapURL", getSourceMapURL, setSourceMapURL),
+    JS_PS_END};
+
+const JSFunctionSpec DebuggerSource::methods_[] = {
+    JS_DEBUG_FN("reparse", reparse, 0), JS_FS_END};
diff --git a/js/src/debugger/Source.h b/js/src/debugger/Source.h
new file mode 100644
index 0000000000..831921e63f
--- /dev/null
+++ b/js/src/debugger/Source.h
@@ -0,0 +1,66 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef dbg_Source_h
+#define dbg_Source_h
+
+#include "jsapi.h"
+
+#include "NamespaceImports.h"   // for Value, HandleObject, CallArgs
+#include "debugger/Debugger.h"  // for DebuggerSourceReferent
+#include "gc/Rooting.h"         // for HandleNativeObject
+#include "vm/NativeObject.h"    // for NativeObject
+
+namespace js {
+class GlobalObject;
+}
+
+namespace js {
+
+class DebuggerSource : public NativeObject {
+ public:
+  static const JSClass class_;
+
+  enum {
+    OWNER_SLOT,
+    TEXT_SLOT,
+    RESERVED_SLOTS,
+  };
+
+  static NativeObject* initClass(JSContext* cx, Handle<GlobalObject*> global,
+                                 HandleObject debugCtor);
+  static DebuggerSource* create(JSContext* cx, HandleObject proto,
+                                Handle<DebuggerSourceReferent> referent,
+                                HandleNativeObject debugger);
+
+  void trace(JSTracer* trc);
+
+  using ReferentVariant = DebuggerSourceReferent;
+
+  NativeObject* getReferentRawObject() const;
+  DebuggerSourceReferent getReferent() const;
+
+  static DebuggerSource* check(JSContext* cx, HandleValue v);
+  static bool construct(JSContext* cx, unsigned argc, Value* vp);
+
+  struct CallData;
+
+  // The Debugger.Source.prototype object also has a class of
+  // DebuggerSource::class_ so we differentiate instances from the prototype
+  // based on the presence of an owner debugger.
+  bool isInstance() const { return !getReservedSlot(OWNER_SLOT).isUndefined(); }
+  Debugger* owner() const;
+
+ private:
+  static const JSClassOps classOps_;
+
+  static const JSPropertySpec properties_[];
+  static const JSFunctionSpec methods_[];
+};
+
+} /* namespace js */
+
+#endif /* dbg_Source_h */
diff --git a/js/src/debugger/moz.build b/js/src/debugger/moz.build
new file mode 100644
index 0000000000..c8c162bcbd
--- /dev/null
+++ b/js/src/debugger/moz.build
@@ -0,0 +1,31 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# We give js/src/debugger its own moz.build file, separate from
+# js/src/moz.build, so that the object file names don't conflict with those from
+# other directories. For example, js/src/debugger/Object.cpp and
+# js/src/builtin/Object.cpp had better not smash each other's .o files when
+# unified sources are disabled.
+
+FINAL_LIBRARY = "js"
+
+# Includes should be relative to parent path
+LOCAL_INCLUDES += ["!..", ".."]
+
+include("../js-config.mozbuild")
+include("../js-cxxflags.mozbuild")
+
+UNIFIED_SOURCES = [
+    "Debugger.cpp",
+    "DebuggerMemory.cpp",
+    "DebugScript.cpp",
+    "Environment.cpp",
+    "Frame.cpp",
+    "NoExecute.cpp",
+    "Object.cpp",
+    "Script.cpp",
+    "Source.cpp",
+]