Adding upstream version 124.0.1.upstream/124.0.1

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

1 files changed, 2448 insertions, 0 deletions

diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
new file mode 100644
index 0000000000..1d2eb16885
--- /dev/null
+++ b/dom/base/nsJSEnvironment.cpp
@@ -0,0 +1,2448 @@
+/* -*- 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 "nsError.h"
+#include "nsJSEnvironment.h"
+#include "nsIScriptGlobalObject.h"
+#include "nsIScriptObjectPrincipal.h"
+#include "nsPIDOMWindow.h"
+#include "nsDOMCID.h"
+#include "nsIXPConnect.h"
+#include "nsCOMPtr.h"
+#include "nsISupportsPrimitives.h"
+#include "nsReadableUtils.h"
+#include "nsDOMJSUtils.h"
+#include "nsJSUtils.h"
+#include "nsIDocShell.h"
+#include "nsIDocShellTreeItem.h"
+#include "nsPresContext.h"
+#include "nsIConsoleService.h"
+#include "nsIInterfaceRequestor.h"
+#include "nsIInterfaceRequestorUtils.h"
+#include "nsIObserverService.h"
+#include "nsITimer.h"
+#include "nsAtom.h"
+#include "nsContentUtils.h"
+#include "mozilla/EventDispatcher.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "nsIContent.h"
+#include "nsCycleCollector.h"
+#include "nsXPCOMCIDInternal.h"
+#include "nsServiceManagerUtils.h"
+#include "nsTextFormatter.h"
+#ifdef XP_WIN
+#  include <process.h>
+#  define getpid _getpid
+#else
+#  include <unistd.h>  // for getpid()
+#endif
+#include "xpcpublic.h"
+
+#include "jsapi.h"
+#include "js/Array.h"               // JS::NewArrayObject
+#include "js/PropertyAndElement.h"  // JS_DefineProperty
+#include "js/PropertySpec.h"
+#include "js/SliceBudget.h"
+#include "js/Wrapper.h"
+#include "nsIArray.h"
+#include "CCGCScheduler.h"
+#include "WrapperFactory.h"
+#include "nsGlobalWindowInner.h"
+#include "nsGlobalWindowOuter.h"
+#include "mozilla/AutoRestore.h"
+#include "mozilla/BasePrincipal.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/SchedulerGroup.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_javascript.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/dom/BrowsingContext.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/DOMExceptionBinding.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/ErrorEvent.h"
+#include "mozilla/dom/FetchUtil.h"
+#include "mozilla/dom/RootedDictionary.h"
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/SerializedStackHolder.h"
+#include "mozilla/CycleCollectedJSRuntime.h"
+#include "nsRefreshDriver.h"
+#include "nsJSPrincipals.h"
+#include "AccessCheck.h"
+#include "mozilla/Logging.h"
+#include "prthread.h"
+
+#include "mozilla/Preferences.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/dom/BindingUtils.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/dom/CanvasRenderingContext2DBinding.h"
+#include "mozilla/ContentEvents.h"
+#include "mozilla/CycleCollectedJSContext.h"
+#include "nsCycleCollectionNoteRootCallback.h"
+#include "nsViewManager.h"
+#include "mozilla/EventStateManager.h"
+#include "mozilla/ProfilerLabels.h"
+#include "mozilla/ProfilerMarkers.h"
+#if defined(MOZ_MEMORY)
+#  include "mozmemory.h"
+#endif
+
+using namespace mozilla;
+using namespace mozilla::dom;
+
+// Thank you Microsoft!
+#ifdef CompareString
+#  undef CompareString
+#endif
+
+static JS::GCSliceCallback sPrevGCSliceCallback;
+
+static bool sIncrementalCC = false;
+
+static bool sIsInitialized;
+static bool sShuttingDown;
+
+static CCGCScheduler* sScheduler = nullptr;
+static std::aligned_storage_t<sizeof(*sScheduler)> sSchedulerStorage;
+
+struct CycleCollectorStats {
+  constexpr CycleCollectorStats() = default;
+  void Init();
+  void Clear();
+  void PrepareForCycleCollection(TimeStamp aNow);
+  void AfterPrepareForCycleCollectionSlice(TimeStamp aDeadline,
+                                           TimeStamp aBeginTime,
+                                           TimeStamp aMaybeAfterGCTime);
+  void AfterCycleCollectionSlice();
+  void AfterSyncForgetSkippable(TimeStamp beginTime);
+  void AfterForgetSkippable(TimeDuration duration, uint32_t aRemovedPurples);
+  void AfterCycleCollection();
+
+  void SendTelemetry(TimeDuration aCCNowDuration, TimeStamp aPrevCCEnd) const;
+  void MaybeLogStats(const CycleCollectorResults& aResults,
+                     uint32_t aCleanups) const;
+  void MaybeNotifyStats(const CycleCollectorResults& aResults,
+                        TimeDuration aCCNowDuration, uint32_t aCleanups) const;
+
+  // Time the current slice began, including any GC finishing.
+  TimeStamp mBeginSliceTime;
+
+  // Time the previous slice of the current CC ended.
+  TimeStamp mEndSliceTime;
+
+  // Time the current cycle collection began.
+  TimeStamp mBeginTime;
+
+  // The longest GC finishing duration for any slice of the current CC.
+  TimeDuration mMaxGCDuration;
+
+  // True if we ran sync forget skippable in any slice of the current CC.
+  bool mRanSyncForgetSkippable = false;
+
+  // Number of suspected objects at the start of the current CC.
+  uint32_t mSuspected = 0;
+
+  // The longest duration spent on sync forget skippable in any slice of the
+  // current CC.
+  TimeDuration mMaxSkippableDuration;
+
+  // The longest pause of any slice in the current CC.
+  TimeDuration mMaxSliceTime;
+
+  // The longest slice time since ClearMaxCCSliceTime() was called.
+  TimeDuration mMaxSliceTimeSinceClear;
+
+  // The total amount of time spent actually running the current CC.
+  TimeDuration mTotalSliceTime;
+
+  // True if we were locked out by the GC in any slice of the current CC.
+  bool mAnyLockedOut = false;
+
+  // A file to dump CC activity to; set by MOZ_CCTIMER environment variable.
+  FILE* mFile = nullptr;
+
+  // In case CC slice was triggered during idle time, set to the end of the idle
+  // period.
+  TimeStamp mIdleDeadline;
+
+  TimeDuration mMinForgetSkippableTime;
+  TimeDuration mMaxForgetSkippableTime;
+  TimeDuration mTotalForgetSkippableTime;
+  uint32_t mForgetSkippableBeforeCC = 0;
+
+  uint32_t mRemovedPurples = 0;
+};
+
+static CycleCollectorStats sCCStats;
+
+static const char* ProcessNameForCollectorLog() {
+  return XRE_GetProcessType() == GeckoProcessType_Default ? "default"
+                                                          : "content";
+}
+
+namespace xpc {
+
+// This handles JS Exceptions (via ExceptionStackOrNull), DOM and XPC
+// Exceptions, and arbitrary values that were associated with a stack by the
+// JS engine when they were thrown, as specified by exceptionStack.
+//
+// Note that the returned stackObj and stackGlobal are _not_ wrapped into the
+// compartment of exceptionValue.
+void FindExceptionStackForConsoleReport(
+    nsPIDOMWindowInner* win, JS::Handle<JS::Value> exceptionValue,
+    JS::Handle<JSObject*> exceptionStack, JS::MutableHandle<JSObject*> stackObj,
+    JS::MutableHandle<JSObject*> stackGlobal) {
+  stackObj.set(nullptr);
+  stackGlobal.set(nullptr);
+
+  if (!exceptionValue.isObject()) {
+    // Use the stack provided by the JS engine, if available. This will not be
+    // a wrapper.
+    if (exceptionStack) {
+      stackObj.set(exceptionStack);
+      stackGlobal.set(JS::GetNonCCWObjectGlobal(exceptionStack));
+    }
+    return;
+  }
+
+  if (win && win->AsGlobal()->IsDying()) {
+    // Pretend like we have no stack, so we don't end up keeping the global
+    // alive via the stack.
+    return;
+  }
+
+  JS::RootingContext* rcx = RootingCx();
+  JS::Rooted<JSObject*> exceptionObject(rcx, &exceptionValue.toObject());
+  if (JSObject* excStack = JS::ExceptionStackOrNull(exceptionObject)) {
+    // At this point we know exceptionObject is a possibly-wrapped
+    // js::ErrorObject that has excStack as stack. excStack might also be a CCW,
+    // but excStack must be same-compartment with the unwrapped ErrorObject.
+    // Return the ErrorObject's global as stackGlobal. This matches what we do
+    // in the ErrorObject's |.stack| getter and ensures stackObj and stackGlobal
+    // are same-compartment.
+    JSObject* unwrappedException = js::UncheckedUnwrap(exceptionObject);
+    stackObj.set(excStack);
+    stackGlobal.set(JS::GetNonCCWObjectGlobal(unwrappedException));
+    return;
+  }
+
+  // It is not a JS Exception, try DOM Exception.
+  RefPtr<Exception> exception;
+  UNWRAP_OBJECT(DOMException, exceptionObject, exception);
+  if (!exception) {
+    // Not a DOM Exception, try XPC Exception.
+    UNWRAP_OBJECT(Exception, exceptionObject, exception);
+    if (!exception) {
+      // As above, use the stack provided by the JS engine, if available.
+      if (exceptionStack) {
+        stackObj.set(exceptionStack);
+        stackGlobal.set(JS::GetNonCCWObjectGlobal(exceptionStack));
+      }
+      return;
+    }
+  }
+
+  nsCOMPtr<nsIStackFrame> stack = exception->GetLocation();
+  if (!stack) {
+    return;
+  }
+  JS::Rooted<JS::Value> value(rcx);
+  stack->GetNativeSavedFrame(&value);
+  if (value.isObject()) {
+    stackObj.set(&value.toObject());
+    MOZ_ASSERT(JS::IsUnwrappedSavedFrame(stackObj));
+    stackGlobal.set(JS::GetNonCCWObjectGlobal(stackObj));
+    return;
+  }
+}
+
+} /* namespace xpc */
+
+static TimeDuration GetCollectionTimeDelta() {
+  static TimeStamp sFirstCollectionTime;
+  TimeStamp now = TimeStamp::Now();
+  if (sFirstCollectionTime) {
+    return now - sFirstCollectionTime;
+  }
+  sFirstCollectionTime = now;
+  return TimeDuration();
+}
+
+class nsJSEnvironmentObserver final : public nsIObserver {
+  ~nsJSEnvironmentObserver() = default;
+
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIOBSERVER
+};
+
+NS_IMPL_ISUPPORTS(nsJSEnvironmentObserver, nsIObserver)
+
+NS_IMETHODIMP
+nsJSEnvironmentObserver::Observe(nsISupports* aSubject, const char* aTopic,
+                                 const char16_t* aData) {
+  if (!nsCRT::strcmp(aTopic, "memory-pressure")) {
+    if (StaticPrefs::javascript_options_gc_on_memory_pressure()) {
+      if (sShuttingDown) {
+        // Don't GC/CC if we're already shutting down.
+        return NS_OK;
+      }
+      nsDependentString data(aData);
+      if (data.EqualsLiteral("low-memory-ongoing")) {
+        // Don't GC/CC if we are in an ongoing low-memory state since its very
+        // slow and it likely won't help us anyway.
+        return NS_OK;
+      }
+      if (data.EqualsLiteral("heap-minimize")) {
+        // heap-minimize notifiers expect this to run synchronously
+        nsJSContext::DoLowMemoryGC();
+        return NS_OK;
+      }
+      if (data.EqualsLiteral("low-memory")) {
+        nsJSContext::SetLowMemoryState(true);
+      }
+      // Asynchronously GC.
+      nsJSContext::LowMemoryGC();
+    }
+  } else if (!nsCRT::strcmp(aTopic, "memory-pressure-stop")) {
+    nsJSContext::SetLowMemoryState(false);
+  } else if (!nsCRT::strcmp(aTopic, "user-interaction-inactive")) {
+    sScheduler->UserIsInactive();
+  } else if (!nsCRT::strcmp(aTopic, "user-interaction-active")) {
+    sScheduler->UserIsActive();
+  } else if (!nsCRT::strcmp(aTopic, "quit-application") ||
+             !nsCRT::strcmp(aTopic, NS_XPCOM_SHUTDOWN_OBSERVER_ID) ||
+             !nsCRT::strcmp(aTopic, "content-child-will-shutdown")) {
+    sShuttingDown = true;
+    sScheduler->Shutdown();
+  }
+
+  return NS_OK;
+}
+
+/****************************************************************
+ ************************** AutoFree ****************************
+ ****************************************************************/
+
+class AutoFree {
+ public:
+  explicit AutoFree(void* aPtr) : mPtr(aPtr) {}
+  ~AutoFree() {
+    if (mPtr) free(mPtr);
+  }
+  void Invalidate() { mPtr = nullptr; }
+
+ private:
+  void* mPtr;
+};
+
+// A utility function for script languages to call.  Although it looks small,
+// the use of nsIDocShell and nsPresContext triggers a huge number of
+// dependencies that most languages would not otherwise need.
+// XXXmarkh - This function is mis-placed!
+bool NS_HandleScriptError(nsIScriptGlobalObject* aScriptGlobal,
+                          const ErrorEventInit& aErrorEventInit,
+                          nsEventStatus* aStatus) {
+  bool called = false;
+  nsCOMPtr<nsPIDOMWindowInner> win(do_QueryInterface(aScriptGlobal));
+  nsIDocShell* docShell = win ? win->GetDocShell() : nullptr;
+  if (docShell) {
+    RefPtr<nsPresContext> presContext = docShell->GetPresContext();
+
+    static int32_t errorDepth;  // Recursion prevention
+    ++errorDepth;
+
+    if (errorDepth < 2) {
+      // Dispatch() must be synchronous for the recursion block
+      // (errorDepth) to work.
+      RefPtr<ErrorEvent> event = ErrorEvent::Constructor(
+          nsGlobalWindowInner::Cast(win), u"error"_ns, aErrorEventInit);
+      event->SetTrusted(true);
+
+      // MOZ_KnownLive due to bug 1506441
+      EventDispatcher::DispatchDOMEvent(
+          MOZ_KnownLive(nsGlobalWindowInner::Cast(win)), nullptr, event,
+          presContext, aStatus);
+      called = true;
+    }
+    --errorDepth;
+  }
+  return called;
+}
+
+class ScriptErrorEvent : public Runnable {
+ public:
+  ScriptErrorEvent(nsPIDOMWindowInner* aWindow, JS::RootingContext* aRootingCx,
+                   xpc::ErrorReport* aReport, JS::Handle<JS::Value> aError,
+                   JS::Handle<JSObject*> aErrorStack)
+      : mozilla::Runnable("ScriptErrorEvent"),
+        mWindow(aWindow),
+        mReport(aReport),
+        mError(aRootingCx, aError),
+        mErrorStack(aRootingCx, aErrorStack) {}
+
+  // TODO: Convert this to MOZ_CAN_RUN_SCRIPT (bug 1415230, bug 1535398)
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY NS_IMETHOD Run() override {
+    nsEventStatus status = nsEventStatus_eIgnore;
+    nsCOMPtr<nsPIDOMWindowInner> win = mWindow;
+    MOZ_ASSERT(win);
+    MOZ_ASSERT(NS_IsMainThread());
+    // First, notify the DOM that we have a script error, but only if
+    // our window is still the current inner.
+    JS::RootingContext* rootingCx = RootingCx();
+    if (win->IsCurrentInnerWindow() && win->GetDocShell() &&
+        !sHandlingScriptError) {
+      AutoRestore<bool> recursionGuard(sHandlingScriptError);
+      sHandlingScriptError = true;
+
+      RefPtr<nsPresContext> presContext = win->GetDocShell()->GetPresContext();
+
+      RootedDictionary<ErrorEventInit> init(rootingCx);
+      init.mCancelable = true;
+      init.mFilename = mReport->mFileName;
+      init.mBubbles = true;
+
+      constexpr auto xoriginMsg = u"Script error."_ns;
+      if (!mReport->mIsMuted) {
+        init.mMessage = mReport->mErrorMsg;
+        init.mLineno = mReport->mLineNumber;
+        init.mColno = mReport->mColumn;
+        init.mError = mError;
+      } else {
+        NS_WARNING("Not same origin error!");
+        init.mMessage = xoriginMsg;
+        init.mLineno = 0;
+      }
+
+      RefPtr<ErrorEvent> event = ErrorEvent::Constructor(
+          nsGlobalWindowInner::Cast(win), u"error"_ns, init);
+      event->SetTrusted(true);
+
+      // MOZ_KnownLive due to bug 1506441
+      EventDispatcher::DispatchDOMEvent(
+          MOZ_KnownLive(nsGlobalWindowInner::Cast(win)), nullptr, event,
+          presContext, &status);
+    }
+
+    if (status != nsEventStatus_eConsumeNoDefault) {
+      JS::Rooted<JSObject*> stack(rootingCx);
+      JS::Rooted<JSObject*> stackGlobal(rootingCx);
+      xpc::FindExceptionStackForConsoleReport(win, mError, mErrorStack, &stack,
+                                              &stackGlobal);
+      JS::Rooted<Maybe<JS::Value>> exception(rootingCx, Some(mError));
+      nsGlobalWindowInner* inner = nsGlobalWindowInner::Cast(win);
+      mReport->LogToConsoleWithStack(inner, exception, stack, stackGlobal);
+    }
+
+    return NS_OK;
+  }
+
+ private:
+  nsCOMPtr<nsPIDOMWindowInner> mWindow;
+  RefPtr<xpc::ErrorReport> mReport;
+  JS::PersistentRooted<JS::Value> mError;
+  JS::PersistentRooted<JSObject*> mErrorStack;
+
+  static bool sHandlingScriptError;
+};
+
+bool ScriptErrorEvent::sHandlingScriptError = false;
+
+// This temporarily lives here to avoid code churn. It will go away entirely
+// soon.
+namespace xpc {
+
+void DispatchScriptErrorEvent(nsPIDOMWindowInner* win,
+                              JS::RootingContext* rootingCx,
+                              xpc::ErrorReport* xpcReport,
+                              JS::Handle<JS::Value> exception,
+                              JS::Handle<JSObject*> exceptionStack) {
+  nsContentUtils::AddScriptRunner(new ScriptErrorEvent(
+      win, rootingCx, xpcReport, exception, exceptionStack));
+}
+
+} /* namespace xpc */
+
+#ifdef DEBUG
+// A couple of useful functions to call when you're debugging.
+nsGlobalWindowInner* JSObject2Win(JSObject* obj) {
+  return xpc::WindowOrNull(obj);
+}
+
+template <typename T>
+void PrintWinURI(T* win) {
+  if (!win) {
+    printf("No window passed in.\n");
+    return;
+  }
+
+  nsCOMPtr<Document> doc = win->GetExtantDoc();
+  if (!doc) {
+    printf("No document in the window.\n");
+    return;
+  }
+
+  nsIURI* uri = doc->GetDocumentURI();
+  if (!uri) {
+    printf("Document doesn't have a URI.\n");
+    return;
+  }
+
+  printf("%s\n", uri->GetSpecOrDefault().get());
+}
+
+void PrintWinURIInner(nsGlobalWindowInner* aWin) { return PrintWinURI(aWin); }
+
+void PrintWinURIOuter(nsGlobalWindowOuter* aWin) { return PrintWinURI(aWin); }
+
+template <typename T>
+void PrintWinCodebase(T* win) {
+  if (!win) {
+    printf("No window passed in.\n");
+    return;
+  }
+
+  nsIPrincipal* prin = win->GetPrincipal();
+  if (!prin) {
+    printf("Window doesn't have principals.\n");
+    return;
+  }
+  if (prin->IsSystemPrincipal()) {
+    printf("No URI, it's the system principal.\n");
+    return;
+  }
+  nsCString spec;
+  prin->GetAsciiSpec(spec);
+  printf("%s\n", spec.get());
+}
+
+void PrintWinCodebaseInner(nsGlobalWindowInner* aWin) {
+  return PrintWinCodebase(aWin);
+}
+
+void PrintWinCodebaseOuter(nsGlobalWindowOuter* aWin) {
+  return PrintWinCodebase(aWin);
+}
+
+void DumpString(const nsAString& str) {
+  printf("%s\n", NS_ConvertUTF16toUTF8(str).get());
+}
+#endif
+
+nsJSContext::nsJSContext(bool aGCOnDestruction,
+                         nsIScriptGlobalObject* aGlobalObject)
+    : mWindowProxy(nullptr),
+      mGCOnDestruction(aGCOnDestruction),
+      mGlobalObjectRef(aGlobalObject) {
+  EnsureStatics();
+
+  mProcessingScriptTag = false;
+  HoldJSObjects(this);
+}
+
+nsJSContext::~nsJSContext() {
+  mGlobalObjectRef = nullptr;
+
+  Destroy();
+}
+
+void nsJSContext::Destroy() {
+  if (mGCOnDestruction) {
+    sScheduler->PokeGC(JS::GCReason::NSJSCONTEXT_DESTROY, mWindowProxy);
+  }
+
+  DropJSObjects(this);
+}
+
+// QueryInterface implementation for nsJSContext
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsJSContext)
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsJSContext)
+  NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mWindowProxy)
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsJSContext)
+  tmp->mGCOnDestruction = false;
+  tmp->mWindowProxy = nullptr;
+  tmp->Destroy();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mGlobalObjectRef)
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsJSContext)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mGlobalObjectRef)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsJSContext)
+  NS_INTERFACE_MAP_ENTRY(nsIScriptContext)
+  NS_INTERFACE_MAP_ENTRY(nsISupports)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsJSContext)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsJSContext)
+
+#ifdef DEBUG
+bool AtomIsEventHandlerName(nsAtom* aName) {
+  const char16_t* name = aName->GetUTF16String();
+
+  const char16_t* cp;
+  char16_t c;
+  for (cp = name; *cp != '\0'; ++cp) {
+    c = *cp;
+    if ((c < 'A' || c > 'Z') && (c < 'a' || c > 'z')) return false;
+  }
+
+  return true;
+}
+#endif
+
+nsIScriptGlobalObject* nsJSContext::GetGlobalObject() {
+  // Note: this could probably be simplified somewhat more; see bug 974327
+  // comments 1 and 3.
+  if (!mWindowProxy) {
+    return nullptr;
+  }
+
+  MOZ_ASSERT(mGlobalObjectRef);
+  return mGlobalObjectRef;
+}
+
+nsresult nsJSContext::SetProperty(JS::Handle<JSObject*> aTarget,
+                                  const char* aPropName, nsISupports* aArgs) {
+  AutoJSAPI jsapi;
+  if (NS_WARN_IF(!jsapi.Init(GetGlobalObject()))) {
+    return NS_ERROR_FAILURE;
+  }
+  JSContext* cx = jsapi.cx();
+
+  JS::RootedVector<JS::Value> args(cx);
+
+  JS::Rooted<JSObject*> global(cx, GetWindowProxy());
+  nsresult rv = ConvertSupportsTojsvals(cx, aArgs, global, &args);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  // got the arguments, now attach them.
+
+  for (uint32_t i = 0; i < args.length(); ++i) {
+    if (!JS_WrapValue(cx, args[i])) {
+      return NS_ERROR_FAILURE;
+    }
+  }
+
+  JS::Rooted<JSObject*> array(cx, JS::NewArrayObject(cx, args));
+  if (!array) {
+    return NS_ERROR_FAILURE;
+  }
+
+  return JS_DefineProperty(cx, aTarget, aPropName, array, 0) ? NS_OK
+                                                             : NS_ERROR_FAILURE;
+}
+
+nsresult nsJSContext::ConvertSupportsTojsvals(
+    JSContext* aCx, nsISupports* aArgs, JS::Handle<JSObject*> aScope,
+    JS::MutableHandleVector<JS::Value> aArgsOut) {
+  nsresult rv = NS_OK;
+
+  // If the array implements nsIJSArgArray, copy the contents and return.
+  nsCOMPtr<nsIJSArgArray> fastArray = do_QueryInterface(aArgs);
+  if (fastArray) {
+    uint32_t argc;
+    JS::Value* argv;
+    rv = fastArray->GetArgs(&argc, reinterpret_cast<void**>(&argv));
+    if (NS_SUCCEEDED(rv) && !aArgsOut.append(argv, argc)) {
+      rv = NS_ERROR_OUT_OF_MEMORY;
+    }
+    return rv;
+  }
+
+  // Take the slower path converting each item.
+  // Handle only nsIArray and nsIVariant.  nsIArray is only needed for
+  // SetProperty('arguments', ...);
+
+  nsIXPConnect* xpc = nsContentUtils::XPConnect();
+  NS_ENSURE_TRUE(xpc, NS_ERROR_UNEXPECTED);
+
+  if (!aArgs) return NS_OK;
+  uint32_t argCount;
+  // This general purpose function may need to convert an arg array
+  // (window.arguments, event-handler args) and a generic property.
+  nsCOMPtr<nsIArray> argsArray(do_QueryInterface(aArgs));
+
+  if (argsArray) {
+    rv = argsArray->GetLength(&argCount);
+    NS_ENSURE_SUCCESS(rv, rv);
+    if (argCount == 0) return NS_OK;
+  } else {
+    argCount = 1;  // the nsISupports which is not an array
+  }
+
+  // Use the caller's auto guards to release and unroot.
+  if (!aArgsOut.resize(argCount)) {
+    return NS_ERROR_OUT_OF_MEMORY;
+  }
+
+  if (argsArray) {
+    for (uint32_t argCtr = 0; argCtr < argCount && NS_SUCCEEDED(rv); argCtr++) {
+      nsCOMPtr<nsISupports> arg;
+      JS::MutableHandle<JS::Value> thisVal = aArgsOut[argCtr];
+      argsArray->QueryElementAt(argCtr, NS_GET_IID(nsISupports),
+                                getter_AddRefs(arg));
+      if (!arg) {
+        thisVal.setNull();
+        continue;
+      }
+      nsCOMPtr<nsIVariant> variant(do_QueryInterface(arg));
+      if (variant != nullptr) {
+        rv = xpc->VariantToJS(aCx, aScope, variant, thisVal);
+      } else {
+        // And finally, support the nsISupportsPrimitives supplied
+        // by the AppShell.  It generally will pass only strings, but
+        // as we have code for handling all, we may as well use it.
+        rv = AddSupportsPrimitiveTojsvals(aCx, arg, thisVal.address());
+        if (rv == NS_ERROR_NO_INTERFACE) {
+          // something else - probably an event object or similar -
+          // just wrap it.
+#ifdef DEBUG
+          // but first, check its not another nsISupportsPrimitive, as
+          // these are now deprecated for use with script contexts.
+          nsCOMPtr<nsISupportsPrimitive> prim(do_QueryInterface(arg));
+          NS_ASSERTION(prim == nullptr,
+                       "Don't pass nsISupportsPrimitives - use nsIVariant!");
+#endif
+          JSAutoRealm ar(aCx, aScope);
+          rv = nsContentUtils::WrapNative(aCx, arg, thisVal);
+        }
+      }
+    }
+  } else {
+    nsCOMPtr<nsIVariant> variant = do_QueryInterface(aArgs);
+    if (variant) {
+      rv = xpc->VariantToJS(aCx, aScope, variant, aArgsOut[0]);
+    } else {
+      NS_ERROR("Not an array, not an interface?");
+      rv = NS_ERROR_UNEXPECTED;
+    }
+  }
+  return rv;
+}
+
+// This really should go into xpconnect somewhere...
+nsresult nsJSContext::AddSupportsPrimitiveTojsvals(JSContext* aCx,
+                                                   nsISupports* aArg,
+                                                   JS::Value* aArgv) {
+  MOZ_ASSERT(aArg, "Empty arg");
+
+  nsCOMPtr<nsISupportsPrimitive> argPrimitive(do_QueryInterface(aArg));
+  if (!argPrimitive) return NS_ERROR_NO_INTERFACE;
+
+  uint16_t type;
+  argPrimitive->GetType(&type);
+
+  switch (type) {
+    case nsISupportsPrimitive::TYPE_CSTRING: {
+      nsCOMPtr<nsISupportsCString> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      nsAutoCString data;
+
+      p->GetData(data);
+
+      JSString* str = ::JS_NewStringCopyN(aCx, data.get(), data.Length());
+      NS_ENSURE_TRUE(str, NS_ERROR_OUT_OF_MEMORY);
+
+      aArgv->setString(str);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_STRING: {
+      nsCOMPtr<nsISupportsString> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      nsAutoString data;
+
+      p->GetData(data);
+
+      // cast is probably safe since wchar_t and char16_t are expected
+      // to be equivalent; both unsigned 16-bit entities
+      JSString* str = ::JS_NewUCStringCopyN(aCx, data.get(), data.Length());
+      NS_ENSURE_TRUE(str, NS_ERROR_OUT_OF_MEMORY);
+
+      aArgv->setString(str);
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRBOOL: {
+      nsCOMPtr<nsISupportsPRBool> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      bool data;
+
+      p->GetData(&data);
+
+      aArgv->setBoolean(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRUINT8: {
+      nsCOMPtr<nsISupportsPRUint8> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      uint8_t data;
+
+      p->GetData(&data);
+
+      aArgv->setInt32(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRUINT16: {
+      nsCOMPtr<nsISupportsPRUint16> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      uint16_t data;
+
+      p->GetData(&data);
+
+      aArgv->setInt32(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRUINT32: {
+      nsCOMPtr<nsISupportsPRUint32> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      uint32_t data;
+
+      p->GetData(&data);
+
+      aArgv->setInt32(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_CHAR: {
+      nsCOMPtr<nsISupportsChar> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      char data;
+
+      p->GetData(&data);
+
+      JSString* str = ::JS_NewStringCopyN(aCx, &data, 1);
+      NS_ENSURE_TRUE(str, NS_ERROR_OUT_OF_MEMORY);
+
+      aArgv->setString(str);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRINT16: {
+      nsCOMPtr<nsISupportsPRInt16> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      int16_t data;
+
+      p->GetData(&data);
+
+      aArgv->setInt32(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_PRINT32: {
+      nsCOMPtr<nsISupportsPRInt32> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      int32_t data;
+
+      p->GetData(&data);
+
+      aArgv->setInt32(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_FLOAT: {
+      nsCOMPtr<nsISupportsFloat> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      float data;
+
+      p->GetData(&data);
+
+      *aArgv = ::JS_NumberValue(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_DOUBLE: {
+      nsCOMPtr<nsISupportsDouble> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      double data;
+
+      p->GetData(&data);
+
+      *aArgv = ::JS_NumberValue(data);
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_INTERFACE_POINTER: {
+      nsCOMPtr<nsISupportsInterfacePointer> p(do_QueryInterface(argPrimitive));
+      NS_ENSURE_TRUE(p, NS_ERROR_UNEXPECTED);
+
+      nsCOMPtr<nsISupports> data;
+      nsIID* iid = nullptr;
+
+      p->GetData(getter_AddRefs(data));
+      p->GetDataIID(&iid);
+      NS_ENSURE_TRUE(iid, NS_ERROR_UNEXPECTED);
+
+      AutoFree iidGuard(iid);  // Free iid upon destruction.
+
+      JS::Rooted<JSObject*> scope(aCx, GetWindowProxy());
+      JS::Rooted<JS::Value> v(aCx);
+      JSAutoRealm ar(aCx, scope);
+      nsresult rv = nsContentUtils::WrapNative(aCx, data, iid, &v);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      *aArgv = v;
+
+      break;
+    }
+    case nsISupportsPrimitive::TYPE_ID:
+    case nsISupportsPrimitive::TYPE_PRUINT64:
+    case nsISupportsPrimitive::TYPE_PRINT64:
+    case nsISupportsPrimitive::TYPE_PRTIME: {
+      NS_WARNING("Unsupported primitive type used");
+      aArgv->setNull();
+      break;
+    }
+    default: {
+      NS_WARNING("Unknown primitive type used");
+      aArgv->setNull();
+      break;
+    }
+  }
+  return NS_OK;
+}
+
+#ifdef MOZ_JPROF
+
+#  include <signal.h>
+
+inline bool IsJProfAction(struct sigaction* action) {
+  return (action->sa_sigaction &&
+          (action->sa_flags & (SA_RESTART | SA_SIGINFO)) ==
+              (SA_RESTART | SA_SIGINFO));
+}
+
+void NS_JProfStartProfiling();
+void NS_JProfStopProfiling();
+void NS_JProfClearCircular();
+
+static bool JProfStartProfilingJS(JSContext* cx, unsigned argc, JS::Value* vp) {
+  NS_JProfStartProfiling();
+  return true;
+}
+
+void NS_JProfStartProfiling() {
+  // Figure out whether we're dealing with SIGPROF, SIGALRM, or
+  // SIGPOLL profiling (SIGALRM for JP_REALTIME, SIGPOLL for
+  // JP_RTC_HZ)
+  struct sigaction action;
+
+  // Must check ALRM before PROF since both are enabled for real-time
+  sigaction(SIGALRM, nullptr, &action);
+  // printf("SIGALRM: %p, flags = %x\n",action.sa_sigaction,action.sa_flags);
+  if (IsJProfAction(&action)) {
+    // printf("Beginning real-time jprof profiling.\n");
+    raise(SIGALRM);
+    return;
+  }
+
+  sigaction(SIGPROF, nullptr, &action);
+  // printf("SIGPROF: %p, flags = %x\n",action.sa_sigaction,action.sa_flags);
+  if (IsJProfAction(&action)) {
+    // printf("Beginning process-time jprof profiling.\n");
+    raise(SIGPROF);
+    return;
+  }
+
+  sigaction(SIGPOLL, nullptr, &action);
+  // printf("SIGPOLL: %p, flags = %x\n",action.sa_sigaction,action.sa_flags);
+  if (IsJProfAction(&action)) {
+    // printf("Beginning rtc-based jprof profiling.\n");
+    raise(SIGPOLL);
+    return;
+  }
+
+  printf("Could not start jprof-profiling since JPROF_FLAGS was not set.\n");
+}
+
+static bool JProfStopProfilingJS(JSContext* cx, unsigned argc, JS::Value* vp) {
+  NS_JProfStopProfiling();
+  return true;
+}
+
+void NS_JProfStopProfiling() {
+  raise(SIGUSR1);
+  // printf("Stopped jprof profiling.\n");
+}
+
+static bool JProfClearCircularJS(JSContext* cx, unsigned argc, JS::Value* vp) {
+  NS_JProfClearCircular();
+  return true;
+}
+
+void NS_JProfClearCircular() {
+  raise(SIGUSR2);
+  // printf("cleared jprof buffer\n");
+}
+
+static bool JProfSaveCircularJS(JSContext* cx, unsigned argc, JS::Value* vp) {
+  // Not ideal...
+  NS_JProfStopProfiling();
+  NS_JProfStartProfiling();
+  return true;
+}
+
+static const JSFunctionSpec JProfFunctions[] = {
+    JS_FN("JProfStartProfiling", JProfStartProfilingJS, 0, 0),
+    JS_FN("JProfStopProfiling", JProfStopProfilingJS, 0, 0),
+    JS_FN("JProfClearCircular", JProfClearCircularJS, 0, 0),
+    JS_FN("JProfSaveCircular", JProfSaveCircularJS, 0, 0), JS_FS_END};
+
+#endif /* defined(MOZ_JPROF) */
+
+nsresult nsJSContext::InitClasses(JS::Handle<JSObject*> aGlobalObj) {
+  AutoJSAPI jsapi;
+  jsapi.Init();
+  JSContext* cx = jsapi.cx();
+  JSAutoRealm ar(cx, aGlobalObj);
+
+#ifdef MOZ_JPROF
+  // Attempt to initialize JProf functions
+  ::JS_DefineFunctions(cx, aGlobalObj, JProfFunctions);
+#endif
+
+  return NS_OK;
+}
+
+bool nsJSContext::GetProcessingScriptTag() { return mProcessingScriptTag; }
+
+void nsJSContext::SetProcessingScriptTag(bool aFlag) {
+  mProcessingScriptTag = aFlag;
+}
+
+// static
+void nsJSContext::SetLowMemoryState(bool aState) {
+  JSContext* cx = danger::GetJSContext();
+  JS::SetLowMemoryState(cx, aState);
+}
+
+static void GarbageCollectImpl(JS::GCReason aReason,
+                               nsJSContext::IsShrinking aShrinking,
+                               const js::SliceBudget& aBudget) {
+  AUTO_PROFILER_LABEL_DYNAMIC_CSTR_NONSENSITIVE(
+      "nsJSContext::GarbageCollectNow", GCCC, JS::ExplainGCReason(aReason));
+
+  bool wantIncremental = !aBudget.isUnlimited();
+
+  // We use danger::GetJSContext() since AutoJSAPI will assert if the current
+  // thread's context is null (such as during shutdown).
+  JSContext* cx = danger::GetJSContext();
+
+  if (!nsContentUtils::XPConnect() || !cx) {
+    return;
+  }
+
+  if (sScheduler->InIncrementalGC() && wantIncremental) {
+    // We're in the middle of incremental GC. Do another slice.
+    JS::PrepareForIncrementalGC(cx);
+    JS::IncrementalGCSlice(cx, aReason, aBudget);
+    return;
+  }
+
+  JS::GCOptions options = aShrinking == nsJSContext::ShrinkingGC
+                              ? JS::GCOptions::Shrink
+                              : JS::GCOptions::Normal;
+
+  if (!wantIncremental || aReason == JS::GCReason::FULL_GC_TIMER) {
+    sScheduler->SetNeedsFullGC();
+  }
+
+  if (sScheduler->NeedsFullGC()) {
+    JS::PrepareForFullGC(cx);
+  }
+
+  if (wantIncremental) {
+    // Incremental GC slices will be triggered by the GC Runner. If one doesn't
+    // already exist, create it in the GC_SLICE_END callback for the first
+    // slice being executed here.
+    JS::StartIncrementalGC(cx, options, aReason, aBudget);
+  } else {
+    JS::NonIncrementalGC(cx, options, aReason);
+  }
+}
+
+// static
+void nsJSContext::GarbageCollectNow(JS::GCReason aReason,
+                                    IsShrinking aShrinking) {
+  GarbageCollectImpl(aReason, aShrinking, js::SliceBudget::unlimited());
+}
+
+// static
+void nsJSContext::RunIncrementalGCSlice(JS::GCReason aReason,
+                                        IsShrinking aShrinking,
+                                        js::SliceBudget& aBudget) {
+  AUTO_PROFILER_LABEL_RELEVANT_FOR_JS("Incremental GC", GCCC);
+  GarbageCollectImpl(aReason, aShrinking, aBudget);
+}
+
+static void FinishAnyIncrementalGC() {
+  AUTO_PROFILER_LABEL("FinishAnyIncrementalGC", GCCC);
+
+  if (sScheduler->InIncrementalGC()) {
+    AutoJSAPI jsapi;
+    jsapi.Init();
+
+    // We're in the middle of an incremental GC, so finish it.
+    JS::PrepareForIncrementalGC(jsapi.cx());
+    JS::FinishIncrementalGC(jsapi.cx(), JS::GCReason::CC_FORCED);
+  }
+}
+
+namespace geckoprofiler::markers {
+class CCSliceMarker : public BaseMarkerType<CCSliceMarker> {
+ public:
+  static constexpr const char* Name = "CCSlice";
+  static constexpr const char* Description =
+      "Information for an individual CC slice.";
+
+  using MS = MarkerSchema;
+  static constexpr MS::PayloadField PayloadFields[] = {
+      {"idle", MS::InputType::Boolean, "Idle", MS::Format::Integer}};
+
+  static constexpr MS::Location Locations[] = {MS::Location::MarkerChart,
+                                               MS::Location::MarkerTable,
+                                               MS::Location::TimelineMemory};
+  static constexpr const char* AllLabels =
+      "{marker.name} (idle={marker.data.idle})";
+
+  static constexpr MS::ETWMarkerGroup Group = MS::ETWMarkerGroup::Memory;
+
+  static void StreamJSONMarkerData(
+      mozilla::baseprofiler::SpliceableJSONWriter& aWriter,
+      bool aIsDuringIdle) {
+    StreamJSONMarkerDataImpl(aWriter, aIsDuringIdle);
+  }
+};
+}  // namespace geckoprofiler::markers
+
+static void FireForgetSkippable(bool aRemoveChildless, TimeStamp aDeadline) {
+  TimeStamp startTimeStamp = TimeStamp::Now();
+  FinishAnyIncrementalGC();
+
+  uint32_t suspectedBefore = nsCycleCollector_suspectedCount();
+  js::SliceBudget budget =
+      sScheduler->ComputeForgetSkippableBudget(startTimeStamp, aDeadline);
+  bool earlyForgetSkippable = sScheduler->IsEarlyForgetSkippable();
+  nsCycleCollector_forgetSkippable(budget, aRemoveChildless,
+                                   earlyForgetSkippable);
+  TimeStamp now = TimeStamp::Now();
+  uint32_t removedPurples = sScheduler->NoteForgetSkippableComplete(
+      now, suspectedBefore, nsCycleCollector_suspectedCount());
+
+  TimeDuration duration = now - startTimeStamp;
+
+  sCCStats.AfterForgetSkippable(duration, removedPurples);
+
+  if (duration.ToSeconds()) {
+    TimeDuration idleDuration;
+    if (!aDeadline.IsNull()) {
+      if (aDeadline < now) {
+        // This slice overflowed the idle period.
+        if (aDeadline > startTimeStamp) {
+          idleDuration = aDeadline - startTimeStamp;
+        }
+      } else {
+        idleDuration = duration;
+      }
+    }
+
+    uint32_t percent =
+        uint32_t(idleDuration.ToSeconds() / duration.ToSeconds() * 100);
+    Telemetry::Accumulate(Telemetry::FORGET_SKIPPABLE_DURING_IDLE, percent);
+  }
+
+  PROFILER_MARKER("ForgetSkippable", GCCC,
+                  MarkerTiming::IntervalUntilNowFrom(startTimeStamp),
+                  CCSliceMarker, !aDeadline.IsNull());
+}
+
+MOZ_ALWAYS_INLINE
+static TimeDuration TimeBetween(TimeStamp aStart, TimeStamp aEnd) {
+  MOZ_ASSERT(aEnd >= aStart);
+  return aEnd - aStart;
+}
+
+static TimeDuration TimeUntilNow(TimeStamp start) {
+  if (start.IsNull()) {
+    return TimeDuration();
+  }
+  return TimeBetween(start, TimeStamp::Now());
+}
+
+void CycleCollectorStats::Init() {
+  Clear();
+
+  char* env = getenv("MOZ_CCTIMER");
+  if (!env) {
+    return;
+  }
+  if (strcmp(env, "none") == 0) {
+    mFile = nullptr;
+  } else if (strcmp(env, "stdout") == 0) {
+    mFile = stdout;
+  } else if (strcmp(env, "stderr") == 0) {
+    mFile = stderr;
+  } else {
+    mFile = fopen(env, "a");
+    if (!mFile) {
+      MOZ_CRASH("Failed to open MOZ_CCTIMER log file.");
+    }
+  }
+}
+
+void CycleCollectorStats::Clear() {
+  if (mFile && mFile != stdout && mFile != stderr) {
+    fclose(mFile);
+  }
+  *this = CycleCollectorStats();
+}
+
+void CycleCollectorStats::AfterCycleCollectionSlice() {
+  if (mBeginSliceTime.IsNull()) {
+    // We already called this method from EndCycleCollectionCallback for this
+    // slice.
+    return;
+  }
+
+  mEndSliceTime = TimeStamp::Now();
+  TimeDuration duration = mEndSliceTime - mBeginSliceTime;
+
+  PROFILER_MARKER(
+      "CCSlice", GCCC, MarkerTiming::Interval(mBeginSliceTime, mEndSliceTime),
+      CCSliceMarker, !mIdleDeadline.IsNull() && mIdleDeadline >= mEndSliceTime);
+
+  if (duration.ToSeconds()) {
+    TimeDuration idleDuration;
+    if (!mIdleDeadline.IsNull()) {
+      if (mIdleDeadline < mEndSliceTime) {
+        // This slice overflowed the idle period.
+        if (mIdleDeadline > mBeginSliceTime) {
+          idleDuration = mIdleDeadline - mBeginSliceTime;
+        }
+      } else {
+        idleDuration = duration;
+      }
+    }
+
+    uint32_t percent =
+        uint32_t(idleDuration.ToSeconds() / duration.ToSeconds() * 100);
+    Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_SLICE_DURING_IDLE,
+                          percent);
+  }
+
+  TimeDuration sliceTime = TimeBetween(mBeginSliceTime, mEndSliceTime);
+  mMaxSliceTime = std::max(mMaxSliceTime, sliceTime);
+  mMaxSliceTimeSinceClear = std::max(mMaxSliceTimeSinceClear, sliceTime);
+  mTotalSliceTime += sliceTime;
+  mBeginSliceTime = TimeStamp();
+}
+
+void CycleCollectorStats::PrepareForCycleCollection(TimeStamp aNow) {
+  mBeginTime = aNow;
+  mSuspected = nsCycleCollector_suspectedCount();
+}
+
+void CycleCollectorStats::AfterPrepareForCycleCollectionSlice(
+    TimeStamp aDeadline, TimeStamp aBeginTime, TimeStamp aMaybeAfterGCTime) {
+  mBeginSliceTime = aBeginTime;
+  mIdleDeadline = aDeadline;
+
+  if (!aMaybeAfterGCTime.IsNull()) {
+    mAnyLockedOut = true;
+    mMaxGCDuration = std::max(mMaxGCDuration, aMaybeAfterGCTime - aBeginTime);
+  }
+}
+
+void CycleCollectorStats::AfterSyncForgetSkippable(TimeStamp beginTime) {
+  mMaxSkippableDuration =
+      std::max(mMaxSkippableDuration, TimeUntilNow(beginTime));
+  mRanSyncForgetSkippable = true;
+}
+
+void CycleCollectorStats::AfterForgetSkippable(TimeDuration duration,
+                                               uint32_t aRemovedPurples) {
+  if (!mMinForgetSkippableTime || mMinForgetSkippableTime > duration) {
+    mMinForgetSkippableTime = duration;
+  }
+  if (!mMaxForgetSkippableTime || mMaxForgetSkippableTime < duration) {
+    mMaxForgetSkippableTime = duration;
+  }
+  mTotalForgetSkippableTime += duration;
+  ++mForgetSkippableBeforeCC;
+
+  mRemovedPurples += aRemovedPurples;
+}
+
+void CycleCollectorStats::SendTelemetry(TimeDuration aCCNowDuration,
+                                        TimeStamp aPrevCCEnd) const {
+  Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_FINISH_IGC, mAnyLockedOut);
+  Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_SYNC_SKIPPABLE,
+                        mRanSyncForgetSkippable);
+  Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_FULL,
+                        aCCNowDuration.ToMilliseconds());
+  Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_MAX_PAUSE,
+                        mMaxSliceTime.ToMilliseconds());
+
+  if (!aPrevCCEnd.IsNull()) {
+    TimeDuration timeBetween = TimeBetween(aPrevCCEnd, mBeginTime);
+    Telemetry::Accumulate(Telemetry::CYCLE_COLLECTOR_TIME_BETWEEN,
+                          timeBetween.ToSeconds());
+  }
+
+  Telemetry::Accumulate(Telemetry::FORGET_SKIPPABLE_MAX,
+                        mMaxForgetSkippableTime.ToMilliseconds());
+}
+
+void CycleCollectorStats::MaybeLogStats(const CycleCollectorResults& aResults,
+                                        uint32_t aCleanups) const {
+  if (!StaticPrefs::javascript_options_mem_log() && !sCCStats.mFile) {
+    return;
+  }
+
+  TimeDuration delta = GetCollectionTimeDelta();
+
+  nsCString mergeMsg;
+  if (aResults.mMergedZones) {
+    mergeMsg.AssignLiteral(" merged");
+  }
+
+  nsCString gcMsg;
+  if (aResults.mForcedGC) {
+    gcMsg.AssignLiteral(", forced a GC");
+  }
+
+  const char16_t* kFmt =
+      u"CC(T+%.1f)[%s-%i] max pause: %.fms, total time: %.fms, slices: %lu, "
+      u"suspected: %lu, visited: %lu RCed and %lu%s GCed, collected: %lu "
+      u"RCed and %lu GCed (%lu|%lu|%lu waiting for GC)%s\n"
+      u"ForgetSkippable %lu times before CC, min: %.f ms, max: %.f ms, avg: "
+      u"%.f ms, total: %.f ms, max sync: %.f ms, removed: %lu";
+  nsString msg;
+  nsTextFormatter::ssprintf(
+      msg, kFmt, delta.ToMicroseconds() / PR_USEC_PER_SEC,
+      ProcessNameForCollectorLog(), getpid(), mMaxSliceTime.ToMilliseconds(),
+      mTotalSliceTime.ToMilliseconds(), aResults.mNumSlices, mSuspected,
+      aResults.mVisitedRefCounted, aResults.mVisitedGCed, mergeMsg.get(),
+      aResults.mFreedRefCounted, aResults.mFreedGCed,
+      sScheduler->mCCollectedWaitingForGC,
+      sScheduler->mCCollectedZonesWaitingForGC,
+      sScheduler->mLikelyShortLivingObjectsNeedingGC, gcMsg.get(),
+      mForgetSkippableBeforeCC, mMinForgetSkippableTime.ToMilliseconds(),
+      mMaxForgetSkippableTime.ToMilliseconds(),
+      mTotalForgetSkippableTime.ToMilliseconds() / aCleanups,
+      mTotalForgetSkippableTime.ToMilliseconds(),
+      mMaxSkippableDuration.ToMilliseconds(), mRemovedPurples);
+  if (StaticPrefs::javascript_options_mem_log()) {
+    nsCOMPtr<nsIConsoleService> cs =
+        do_GetService(NS_CONSOLESERVICE_CONTRACTID);
+    if (cs) {
+      cs->LogStringMessage(msg.get());
+    }
+  }
+  if (mFile) {
+    fprintf(mFile, "%s\n", NS_ConvertUTF16toUTF8(msg).get());
+  }
+}
+
+void CycleCollectorStats::MaybeNotifyStats(
+    const CycleCollectorResults& aResults, TimeDuration aCCNowDuration,
+    uint32_t aCleanups) const {
+  if (!StaticPrefs::javascript_options_mem_notify()) {
+    return;
+  }
+
+  const char16_t* kJSONFmt =
+      u"{ \"timestamp\": %llu, "
+      u"\"duration\": %.f, "
+      u"\"max_slice_pause\": %.f, "
+      u"\"total_slice_pause\": %.f, "
+      u"\"max_finish_gc_duration\": %.f, "
+      u"\"max_sync_skippable_duration\": %.f, "
+      u"\"suspected\": %lu, "
+      u"\"visited\": { "
+      u"\"RCed\": %lu, "
+      u"\"GCed\": %lu }, "
+      u"\"collected\": { "
+      u"\"RCed\": %lu, "
+      u"\"GCed\": %lu }, "
+      u"\"waiting_for_gc\": %lu, "
+      u"\"zones_waiting_for_gc\": %lu, "
+      u"\"short_living_objects_waiting_for_gc\": %lu, "
+      u"\"forced_gc\": %d, "
+      u"\"forget_skippable\": { "
+      u"\"times_before_cc\": %lu, "
+      u"\"min\": %.f, "
+      u"\"max\": %.f, "
+      u"\"avg\": %.f, "
+      u"\"total\": %.f, "
+      u"\"removed\": %lu } "
+      u"}";
+
+  nsString json;
+  nsTextFormatter::ssprintf(
+      json, kJSONFmt, PR_Now(), aCCNowDuration.ToMilliseconds(),
+      mMaxSliceTime.ToMilliseconds(), mTotalSliceTime.ToMilliseconds(),
+      mMaxGCDuration.ToMilliseconds(), mMaxSkippableDuration.ToMilliseconds(),
+      mSuspected, aResults.mVisitedRefCounted, aResults.mVisitedGCed,
+      aResults.mFreedRefCounted, aResults.mFreedGCed,
+      sScheduler->mCCollectedWaitingForGC,
+      sScheduler->mCCollectedZonesWaitingForGC,
+      sScheduler->mLikelyShortLivingObjectsNeedingGC, aResults.mForcedGC,
+      mForgetSkippableBeforeCC, mMinForgetSkippableTime.ToMilliseconds(),
+      mMaxForgetSkippableTime.ToMilliseconds(),
+      mTotalForgetSkippableTime.ToMilliseconds() / aCleanups,
+      mTotalForgetSkippableTime.ToMilliseconds(), mRemovedPurples);
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+  if (observerService) {
+    observerService->NotifyObservers(nullptr, "cycle-collection-statistics",
+                                     json.get());
+  }
+}
+
+// static
+void nsJSContext::CycleCollectNow(CCReason aReason,
+                                  nsICycleCollectorListener* aListener) {
+  if (!NS_IsMainThread()) {
+    return;
+  }
+
+  AUTO_PROFILER_LABEL("nsJSContext::CycleCollectNow", GCCC);
+
+  PrepareForCycleCollectionSlice(aReason, TimeStamp());
+  nsCycleCollector_collect(aReason, aListener);
+  sCCStats.AfterCycleCollectionSlice();
+}
+
+// static
+void nsJSContext::PrepareForCycleCollectionSlice(CCReason aReason,
+                                                 TimeStamp aDeadline) {
+  TimeStamp beginTime = TimeStamp::Now();
+
+  // Before we begin the cycle collection, make sure there is no active GC.
+  TimeStamp afterGCTime;
+  if (sScheduler->InIncrementalGC()) {
+    FinishAnyIncrementalGC();
+    afterGCTime = TimeStamp::Now();
+  }
+
+  if (!sScheduler->IsCollectingCycles()) {
+    sCCStats.PrepareForCycleCollection(beginTime);
+    sScheduler->NoteCCBegin(aReason, beginTime,
+                            sCCStats.mForgetSkippableBeforeCC,
+                            sCCStats.mSuspected, sCCStats.mRemovedPurples);
+  }
+
+  sCCStats.AfterPrepareForCycleCollectionSlice(aDeadline, beginTime,
+                                               afterGCTime);
+}
+
+// static
+void nsJSContext::RunCycleCollectorSlice(CCReason aReason,
+                                         TimeStamp aDeadline) {
+  if (!NS_IsMainThread()) {
+    return;
+  }
+
+  PrepareForCycleCollectionSlice(aReason, aDeadline);
+
+  // Decide how long we want to budget for this slice.
+  if (sIncrementalCC) {
+    bool preferShorterSlices;
+    js::SliceBudget budget = sScheduler->ComputeCCSliceBudget(
+        aDeadline, sCCStats.mBeginTime, sCCStats.mEndSliceTime,
+        TimeStamp::Now(), &preferShorterSlices);
+    nsCycleCollector_collectSlice(budget, aReason, preferShorterSlices);
+  } else {
+    js::SliceBudget budget = js::SliceBudget::unlimited();
+    nsCycleCollector_collectSlice(budget, aReason, false);
+  }
+
+  sCCStats.AfterCycleCollectionSlice();
+}
+
+// static
+void nsJSContext::RunCycleCollectorWorkSlice(int64_t aWorkBudget) {
+  if (!NS_IsMainThread()) {
+    return;
+  }
+
+  AUTO_PROFILER_LABEL("nsJSContext::RunCycleCollectorWorkSlice", GCCC);
+
+  PrepareForCycleCollectionSlice(CCReason::API, TimeStamp());
+
+  js::SliceBudget budget = js::SliceBudget(js::WorkBudget(aWorkBudget));
+  nsCycleCollector_collectSlice(budget, CCReason::API);
+
+  sCCStats.AfterCycleCollectionSlice();
+}
+
+void nsJSContext::ClearMaxCCSliceTime() {
+  sCCStats.mMaxSliceTimeSinceClear = TimeDuration();
+}
+
+uint32_t nsJSContext::GetMaxCCSliceTimeSinceClear() {
+  return sCCStats.mMaxSliceTimeSinceClear.ToMilliseconds();
+}
+
+// static
+void nsJSContext::BeginCycleCollectionCallback(CCReason aReason) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  TimeStamp startTime = TimeStamp::Now();
+  sCCStats.PrepareForCycleCollection(startTime);
+
+  // Run forgetSkippable synchronously to reduce the size of the CC graph. This
+  // is particularly useful if we recently finished a GC.
+  if (sScheduler->IsEarlyForgetSkippable()) {
+    while (sScheduler->IsEarlyForgetSkippable()) {
+      FireForgetSkippable(false, TimeStamp());
+    }
+    sCCStats.AfterSyncForgetSkippable(startTime);
+  }
+
+  if (sShuttingDown) {
+    return;
+  }
+
+  sScheduler->InitCCRunnerStateMachine(
+      mozilla::CCGCScheduler::CCRunnerState::CycleCollecting, aReason);
+  sScheduler->EnsureCCRunner(kICCIntersliceDelay, kIdleICCSliceBudget);
+}
+
+// static
+void nsJSContext::EndCycleCollectionCallback(
+    const CycleCollectorResults& aResults) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  sScheduler->KillCCRunner();
+
+  // Update timing information for the current slice before we log it, if
+  // we previously called PrepareForCycleCollectionSlice(). During shutdown
+  // CCs, this won't happen.
+  sCCStats.AfterCycleCollectionSlice();
+
+  TimeStamp endCCTimeStamp = TimeStamp::Now();
+  TimeDuration ccNowDuration = TimeBetween(sCCStats.mBeginTime, endCCTimeStamp);
+  TimeStamp prevCCEnd = sScheduler->GetLastCCEndTime();
+
+  sScheduler->NoteCCEnd(aResults, endCCTimeStamp, sCCStats.mMaxSliceTime);
+
+  // Log information about the CC via telemetry, JSON and the console.
+
+  sCCStats.SendTelemetry(ccNowDuration, prevCCEnd);
+
+  uint32_t cleanups = std::max(sCCStats.mForgetSkippableBeforeCC, 1u);
+
+  sCCStats.MaybeLogStats(aResults, cleanups);
+
+  sCCStats.MaybeNotifyStats(aResults, ccNowDuration, cleanups);
+
+  // Update global state to indicate we have just run a cycle collection.
+  sCCStats.Clear();
+
+  // If we need a GC after this CC (typically because lots of GCed objects or
+  // zones have been collected in the CC), schedule it.
+
+  if (sScheduler->NeedsGCAfterCC()) {
+    MOZ_ASSERT(
+        TimeDuration::FromMilliseconds(
+            StaticPrefs::javascript_options_gc_delay()) > kMaxICCDuration,
+        "A max duration ICC shouldn't reduce GC delay to 0");
+
+    TimeDuration delay;
+    if (aResults.mFreedGCed > 10000 && aResults.mFreedRefCounted > 10000) {
+      // If we collected lots of objects, trigger the next GC sooner so that
+      // GC can cut JS-to-native edges and native objects can be then deleted.
+      delay = TimeDuration::FromMilliseconds(
+          StaticPrefs::javascript_options_gc_delay_interslice());
+    } else {
+      delay = TimeDuration::FromMilliseconds(
+                  StaticPrefs::javascript_options_gc_delay()) -
+              std::min(ccNowDuration, kMaxICCDuration);
+    }
+
+    sScheduler->PokeGC(JS::GCReason::CC_FINISHED, nullptr, delay);
+  }
+#if defined(MOZ_MEMORY)
+  else if (
+      StaticPrefs::
+          dom_memory_foreground_content_processes_have_larger_page_cache()) {
+    jemalloc_free_dirty_pages();
+  }
+#endif
+}
+
+/* static */
+bool CCGCScheduler::CCRunnerFired(TimeStamp aDeadline) {
+  AUTO_PROFILER_LABEL_RELEVANT_FOR_JS("Incremental CC", GCCC);
+
+  bool didDoWork = false;
+
+  // The CC/GC scheduler (sScheduler) decides what action(s) to take during
+  // this invocation of the CC runner.
+  //
+  // This may be zero, one, or multiple actions. (Zero is when CC is blocked by
+  // incremental GC, or when the scheduler determined that a CC is no longer
+  // needed.) Loop until the scheduler finishes this invocation by returning
+  // `Yield` in step.mYield.
+  CCRunnerStep step;
+  do {
+    step = sScheduler->AdvanceCCRunner(aDeadline, TimeStamp::Now(),
+                                       nsCycleCollector_suspectedCount());
+    switch (step.mAction) {
+      case CCRunnerAction::None:
+        break;
+
+      case CCRunnerAction::MinorGC:
+        JS::MaybeRunNurseryCollection(CycleCollectedJSRuntime::Get()->Runtime(),
+                                      step.mParam.mReason);
+        sScheduler->NoteMinorGCEnd();
+        break;
+
+      case CCRunnerAction::ForgetSkippable:
+        // 'Forget skippable' only, then end this invocation.
+        FireForgetSkippable(bool(step.mParam.mRemoveChildless), aDeadline);
+        break;
+
+      case CCRunnerAction::CleanupContentUnbinder:
+        // Clear content unbinder before the first actual CC slice.
+        Element::ClearContentUnbinder();
+        break;
+
+      case CCRunnerAction::CleanupDeferred:
+        // and if time still permits, perform deferred deletions.
+        nsCycleCollector_doDeferredDeletion();
+        break;
+
+      case CCRunnerAction::CycleCollect:
+        // Cycle collection slice.
+        nsJSContext::RunCycleCollectorSlice(step.mParam.mCCReason, aDeadline);
+        break;
+
+      case CCRunnerAction::StopRunning:
+        // End this CC, either because we have run a cycle collection slice, or
+        // because a CC is no longer needed.
+        sScheduler->KillCCRunner();
+        break;
+    }
+
+    if (step.mAction != CCRunnerAction::None) {
+      didDoWork = true;
+    }
+  } while (step.mYield == CCRunnerYield::Continue);
+
+  return didDoWork;
+}
+
+// static
+bool nsJSContext::HasHadCleanupSinceLastGC() {
+  return sScheduler->IsEarlyForgetSkippable(1);
+}
+
+// static
+void nsJSContext::RunNextCollectorTimer(JS::GCReason aReason,
+                                        mozilla::TimeStamp aDeadline) {
+  sScheduler->RunNextCollectorTimer(aReason, aDeadline);
+}
+
+// static
+void nsJSContext::MaybeRunNextCollectorSlice(nsIDocShell* aDocShell,
+                                             JS::GCReason aReason) {
+  if (!aDocShell || !XRE_IsContentProcess()) {
+    return;
+  }
+
+  BrowsingContext* bc = aDocShell->GetBrowsingContext();
+  if (!bc) {
+    return;
+  }
+
+  BrowsingContext* root = bc->Top();
+  if (bc == root) {
+    // We don't want to run collectors when loading the top level page.
+    return;
+  }
+
+  nsIDocShell* rootDocShell = root->GetDocShell();
+  if (!rootDocShell) {
+    return;
+  }
+
+  Document* rootDocument = rootDocShell->GetDocument();
+  if (!rootDocument ||
+      rootDocument->GetReadyStateEnum() != Document::READYSTATE_COMPLETE ||
+      rootDocument->IsInBackgroundWindow()) {
+    return;
+  }
+
+  PresShell* presShell = rootDocument->GetPresShell();
+  if (!presShell) {
+    return;
+  }
+
+  nsViewManager* vm = presShell->GetViewManager();
+  if (!vm) {
+    return;
+  }
+
+  if (!sScheduler->IsUserActive()) {
+    if (sScheduler->InIncrementalGC() || sScheduler->IsCollectingCycles()) {
+      Maybe<TimeStamp> next = nsRefreshDriver::GetNextTickHint();
+      if (next.isSome()) {
+        // Try to not delay the next RefreshDriver tick, so give a reasonable
+        // deadline for collectors.
+        sScheduler->RunNextCollectorTimer(aReason, next.value());
+      }
+    } else {
+      nsCOMPtr<nsIDocShell> shell = aDocShell;
+      NS_DispatchToCurrentThreadQueue(
+          NS_NewRunnableFunction(
+              "nsJSContext::MaybeRunNextCollectorSlice",
+              [shell] {
+                nsIDocShell::BusyFlags busyFlags = nsIDocShell::BUSY_FLAGS_NONE;
+                shell->GetBusyFlags(&busyFlags);
+                if (busyFlags == nsIDocShell::BUSY_FLAGS_NONE) {
+                  return;
+                }
+
+                // In order to improve performance on the next page, run a minor
+                // GC. The 16ms limit ensures it isn't called all the time if
+                // there are for example multiple iframes loading at the same
+                // time.
+                JS::RunNurseryCollection(
+                    CycleCollectedJSRuntime::Get()->Runtime(),
+                    JS::GCReason::PREPARE_FOR_PAGELOAD,
+                    mozilla::TimeDuration::FromMilliseconds(16));
+              }),
+          EventQueuePriority::Idle);
+    }
+  }
+}
+
+// static
+void nsJSContext::PokeGC(JS::GCReason aReason, JSObject* aObj,
+                         TimeDuration aDelay) {
+  sScheduler->PokeGC(aReason, aObj, aDelay);
+}
+
+// static
+void nsJSContext::MaybePokeGC() {
+  if (sShuttingDown) {
+    return;
+  }
+
+  JSRuntime* rt = CycleCollectedJSRuntime::Get()->Runtime();
+  JS::GCReason reason = JS::WantEagerMinorGC(rt);
+  if (reason != JS::GCReason::NO_REASON) {
+    MOZ_ASSERT(reason == JS::GCReason::EAGER_NURSERY_COLLECTION);
+    sScheduler->PokeMinorGC(reason);
+  }
+
+  // Bug 1772638: For now, only do eager minor GCs. Eager major GCs regress some
+  // benchmarks. Hopefully that will be worked out and this will check for
+  // whether an eager major GC is needed.
+}
+
+void nsJSContext::DoLowMemoryGC() {
+  if (sShuttingDown) {
+    return;
+  }
+  nsJSContext::GarbageCollectNow(JS::GCReason::MEM_PRESSURE,
+                                 nsJSContext::ShrinkingGC);
+  nsJSContext::CycleCollectNow(CCReason::MEM_PRESSURE);
+  if (sScheduler->NeedsGCAfterCC()) {
+    nsJSContext::GarbageCollectNow(JS::GCReason::MEM_PRESSURE,
+                                   nsJSContext::ShrinkingGC);
+  }
+}
+
+// static
+void nsJSContext::LowMemoryGC() {
+  RefPtr<CCGCScheduler::MayGCPromise> mbPromise =
+      CCGCScheduler::MayGCNow(JS::GCReason::MEM_PRESSURE);
+  if (!mbPromise) {
+    // Normally when the promise is null it means that IPC failed, that probably
+    // means that something bad happened, don't bother with the GC.
+    return;
+  }
+  mbPromise->Then(
+      GetMainThreadSerialEventTarget(), __func__,
+      [](bool aIgnored) { DoLowMemoryGC(); },
+      [](mozilla::ipc::ResponseRejectReason r) {});
+}
+
+// static
+void nsJSContext::MaybePokeCC() {
+  sScheduler->MaybePokeCC(TimeStamp::NowLoRes(),
+                          nsCycleCollector_suspectedCount());
+}
+
+static void DOMGCSliceCallback(JSContext* aCx, JS::GCProgress aProgress,
+                               const JS::GCDescription& aDesc) {
+  NS_ASSERTION(NS_IsMainThread(), "GCs must run on the main thread");
+
+  static TimeStamp sCurrentGCStartTime;
+
+  switch (aProgress) {
+    case JS::GC_CYCLE_BEGIN: {
+      // Prevent cycle collections and shrinking during incremental GC.
+      sScheduler->NoteGCBegin(aDesc.reason_);
+      sCurrentGCStartTime = TimeStamp::Now();
+      break;
+    }
+
+    case JS::GC_CYCLE_END: {
+      TimeDuration delta = GetCollectionTimeDelta();
+
+      if (StaticPrefs::javascript_options_mem_log()) {
+        nsString gcstats;
+        gcstats.Adopt(aDesc.formatSummaryMessage(aCx));
+        nsAutoString prefix;
+        nsTextFormatter::ssprintf(prefix, u"GC(T+%.1f)[%s-%i] ",
+                                  delta.ToSeconds(),
+                                  ProcessNameForCollectorLog(), getpid());
+        nsString msg = prefix + gcstats;
+        nsCOMPtr<nsIConsoleService> cs =
+            do_GetService(NS_CONSOLESERVICE_CONTRACTID);
+        if (cs) {
+          cs->LogStringMessage(msg.get());
+        }
+      }
+
+      sScheduler->NoteGCEnd();
+
+      // May need to kill the GC runner
+      sScheduler->KillGCRunner();
+
+      nsJSContext::MaybePokeCC();
+
+#if defined(MOZ_MEMORY)
+      bool freeDirty = false;
+#endif
+      if (aDesc.isZone_) {
+        sScheduler->PokeFullGC();
+      } else {
+#if defined(MOZ_MEMORY)
+        freeDirty = true;
+#endif
+        sScheduler->SetNeedsFullGC(false);
+        sScheduler->KillFullGCTimer();
+      }
+
+      if (sScheduler->IsCCNeeded(TimeStamp::Now(),
+                                 nsCycleCollector_suspectedCount()) !=
+          CCReason::NO_REASON) {
+#if defined(MOZ_MEMORY)
+        // We're likely to free the dirty pages after CC.
+        freeDirty = false;
+#endif
+        nsCycleCollector_dispatchDeferredDeletion();
+      }
+
+      Telemetry::Accumulate(Telemetry::GC_IN_PROGRESS_MS,
+                            TimeUntilNow(sCurrentGCStartTime).ToMilliseconds());
+
+#if defined(MOZ_MEMORY)
+      if (freeDirty &&
+          StaticPrefs::
+              dom_memory_foreground_content_processes_have_larger_page_cache()) {
+        jemalloc_free_dirty_pages();
+      }
+#endif
+      break;
+    }
+
+    case JS::GC_SLICE_BEGIN:
+      break;
+
+    case JS::GC_SLICE_END:
+      sScheduler->NoteGCSliceEnd(aDesc.lastSliceStart(aCx),
+                                 aDesc.lastSliceEnd(aCx));
+
+      if (sShuttingDown) {
+        sScheduler->KillGCRunner();
+      } else {
+        // If incremental GC wasn't triggered by GCTimerFired, we may not have a
+        // runner to ensure all the slices are handled. So, create the runner
+        // here.
+        sScheduler->EnsureOrResetGCRunner();
+      }
+
+      if (sScheduler->IsCCNeeded(TimeStamp::Now(),
+                                 nsCycleCollector_suspectedCount()) !=
+          CCReason::NO_REASON) {
+        nsCycleCollector_dispatchDeferredDeletion();
+      }
+
+      if (StaticPrefs::javascript_options_mem_log()) {
+        nsString gcstats;
+        gcstats.Adopt(aDesc.formatSliceMessage(aCx));
+        nsAutoString prefix;
+        nsTextFormatter::ssprintf(prefix, u"[%s-%i] ",
+                                  ProcessNameForCollectorLog(), getpid());
+        nsString msg = prefix + gcstats;
+        nsCOMPtr<nsIConsoleService> cs =
+            do_GetService(NS_CONSOLESERVICE_CONTRACTID);
+        if (cs) {
+          cs->LogStringMessage(msg.get());
+        }
+      }
+
+      break;
+
+    default:
+      MOZ_CRASH("Unexpected GCProgress value");
+  }
+
+  if (sPrevGCSliceCallback) {
+    (*sPrevGCSliceCallback)(aCx, aProgress, aDesc);
+  }
+}
+
+void nsJSContext::SetWindowProxy(JS::Handle<JSObject*> aWindowProxy) {
+  mWindowProxy = aWindowProxy;
+}
+
+JSObject* nsJSContext::GetWindowProxy() { return mWindowProxy; }
+
+void nsJSContext::LikelyShortLivingObjectCreated() {
+  ++sScheduler->mLikelyShortLivingObjectsNeedingGC;
+}
+
+void mozilla::dom::StartupJSEnvironment() {
+  // initialize all our statics, so that we can restart XPCOM
+  sIsInitialized = false;
+  sShuttingDown = false;
+  sCCStats.Init();
+}
+
+static void SetGCParameter(JSGCParamKey aParam, uint32_t aValue) {
+  AutoJSAPI jsapi;
+  jsapi.Init();
+  JS_SetGCParameter(jsapi.cx(), aParam, aValue);
+}
+
+static void ResetGCParameter(JSGCParamKey aParam) {
+  AutoJSAPI jsapi;
+  jsapi.Init();
+  JS_ResetGCParameter(jsapi.cx(), aParam);
+}
+
+static void SetMemoryPrefChangedCallbackMB(const char* aPrefName,
+                                           void* aClosure) {
+  int32_t prefMB = Preferences::GetInt(aPrefName, -1);
+  // handle overflow and negative pref values
+  CheckedInt<int32_t> prefB = CheckedInt<int32_t>(prefMB) * 1024 * 1024;
+  if (prefB.isValid() && prefB.value() >= 0) {
+    SetGCParameter((JSGCParamKey)(uintptr_t)aClosure, prefB.value());
+  } else {
+    ResetGCParameter((JSGCParamKey)(uintptr_t)aClosure);
+  }
+}
+
+static void SetMemoryNurseryPrefChangedCallback(const char* aPrefName,
+                                                void* aClosure) {
+  int32_t prefKB = Preferences::GetInt(aPrefName, -1);
+  // handle overflow and negative pref values
+  CheckedInt<int32_t> prefB = CheckedInt<int32_t>(prefKB) * 1024;
+  if (prefB.isValid() && prefB.value() >= 0) {
+    SetGCParameter((JSGCParamKey)(uintptr_t)aClosure, prefB.value());
+  } else {
+    ResetGCParameter((JSGCParamKey)(uintptr_t)aClosure);
+  }
+}
+
+static void SetMemoryPrefChangedCallbackInt(const char* aPrefName,
+                                            void* aClosure) {
+  int32_t pref = Preferences::GetInt(aPrefName, -1);
+  // handle overflow and negative pref values
+  if (pref >= 0 && pref < 10000) {
+    SetGCParameter((JSGCParamKey)(uintptr_t)aClosure, pref);
+  } else {
+    ResetGCParameter((JSGCParamKey)(uintptr_t)aClosure);
+  }
+}
+
+static void SetMemoryPrefChangedCallbackBool(const char* aPrefName,
+                                             void* aClosure) {
+  bool pref = Preferences::GetBool(aPrefName);
+  SetGCParameter((JSGCParamKey)(uintptr_t)aClosure, pref);
+}
+
+static void SetMemoryGCSliceTimePrefChangedCallback(const char* aPrefName,
+                                                    void* aClosure) {
+  int32_t pref = Preferences::GetInt(aPrefName, -1);
+  // handle overflow and negative pref values
+  if (pref > 0 && pref < 100000) {
+    sScheduler->SetActiveIntersliceGCBudget(
+        TimeDuration::FromMilliseconds(pref));
+    SetGCParameter(JSGC_SLICE_TIME_BUDGET_MS, pref);
+  } else {
+    ResetGCParameter(JSGC_SLICE_TIME_BUDGET_MS);
+  }
+}
+
+static void SetIncrementalCCPrefChangedCallback(const char* aPrefName,
+                                                void* aClosure) {
+  bool pref = Preferences::GetBool(aPrefName);
+  sIncrementalCC = pref;
+}
+
+class JSDispatchableRunnable final : public Runnable {
+  ~JSDispatchableRunnable() { MOZ_ASSERT(!mDispatchable); }
+
+ public:
+  explicit JSDispatchableRunnable(JS::Dispatchable* aDispatchable)
+      : mozilla::Runnable("JSDispatchableRunnable"),
+        mDispatchable(aDispatchable) {
+    MOZ_ASSERT(mDispatchable);
+  }
+
+ protected:
+  NS_IMETHOD Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+
+    AutoJSAPI jsapi;
+    jsapi.Init();
+
+    JS::Dispatchable::MaybeShuttingDown maybeShuttingDown =
+        sShuttingDown ? JS::Dispatchable::ShuttingDown
+                      : JS::Dispatchable::NotShuttingDown;
+
+    mDispatchable->run(jsapi.cx(), maybeShuttingDown);
+    mDispatchable = nullptr;  // mDispatchable may delete itself
+
+    return NS_OK;
+  }
+
+ private:
+  JS::Dispatchable* mDispatchable;
+};
+
+static bool DispatchToEventLoop(void* closure,
+                                JS::Dispatchable* aDispatchable) {
+  MOZ_ASSERT(!closure);
+
+  // This callback may execute either on the main thread or a random JS-internal
+  // helper thread. This callback can be called during shutdown so we cannot
+  // simply NS_DispatchToMainThread. Failure during shutdown is expected and
+  // properly handled by the JS engine.
+
+  nsCOMPtr<nsIEventTarget> mainTarget = GetMainThreadSerialEventTarget();
+  if (!mainTarget) {
+    return false;
+  }
+
+  RefPtr<JSDispatchableRunnable> r = new JSDispatchableRunnable(aDispatchable);
+  MOZ_ALWAYS_SUCCEEDS(mainTarget->Dispatch(r.forget(), NS_DISPATCH_NORMAL));
+  return true;
+}
+
+static bool ConsumeStream(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                          JS::MimeType aMimeType,
+                          JS::StreamConsumer* aConsumer) {
+  return FetchUtil::StreamResponseToJS(aCx, aObj, aMimeType, aConsumer,
+                                       nullptr);
+}
+
+static js::SliceBudget CreateGCSliceBudget(JS::GCReason aReason,
+                                           int64_t aMillis) {
+  return sScheduler->CreateGCSliceBudget(
+      mozilla::TimeDuration::FromMilliseconds(aMillis), false, false);
+}
+
+void nsJSContext::EnsureStatics() {
+  if (sIsInitialized) {
+    if (!nsContentUtils::XPConnect()) {
+      MOZ_CRASH();
+    }
+    return;
+  }
+
+  // Let's make sure that our main thread is the same as the xpcom main thread.
+  MOZ_ASSERT(NS_IsMainThread());
+
+  sScheduler =
+      new (&sSchedulerStorage) CCGCScheduler();  // Reset the scheduler state.
+
+  AutoJSAPI jsapi;
+  jsapi.Init();
+
+  sPrevGCSliceCallback = JS::SetGCSliceCallback(jsapi.cx(), DOMGCSliceCallback);
+
+  JS::SetCreateGCSliceBudgetCallback(jsapi.cx(), CreateGCSliceBudget);
+
+  JS::InitDispatchToEventLoop(jsapi.cx(), DispatchToEventLoop, nullptr);
+  JS::InitConsumeStreamCallback(jsapi.cx(), ConsumeStream,
+                                FetchUtil::ReportJSStreamError);
+
+  // Set these global xpconnect options...
+  Preferences::RegisterCallbackAndCall(SetMemoryPrefChangedCallbackMB,
+                                       "javascript.options.mem.max",
+                                       (void*)JSGC_MAX_BYTES);
+  Preferences::RegisterCallbackAndCall(SetMemoryNurseryPrefChangedCallback,
+                                       "javascript.options.mem.nursery.min_kb",
+                                       (void*)JSGC_MIN_NURSERY_BYTES);
+  Preferences::RegisterCallbackAndCall(SetMemoryNurseryPrefChangedCallback,
+                                       "javascript.options.mem.nursery.max_kb",
+                                       (void*)JSGC_MAX_NURSERY_BYTES);
+
+  Preferences::RegisterCallbackAndCall(SetMemoryPrefChangedCallbackBool,
+                                       "javascript.options.mem.gc_per_zone",
+                                       (void*)JSGC_PER_ZONE_GC_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(SetMemoryPrefChangedCallbackBool,
+                                       "javascript.options.mem.gc_incremental",
+                                       (void*)JSGC_INCREMENTAL_GC_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(SetMemoryPrefChangedCallbackBool,
+                                       "javascript.options.mem.gc_compacting",
+                                       (void*)JSGC_COMPACTING_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackBool,
+      "javascript.options.mem.gc_parallel_marking",
+      (void*)JSGC_PARALLEL_MARKING_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_parallel_marking_threshold_mb",
+      (void*)JSGC_PARALLEL_MARKING_THRESHOLD_MB);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryGCSliceTimePrefChangedCallback,
+      "javascript.options.mem.gc_incremental_slice_ms");
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackBool,
+      "javascript.options.mem.incremental_weakmap",
+      (void*)JSGC_INCREMENTAL_WEAKMAP_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_high_frequency_time_limit_ms",
+      (void*)JSGC_HIGH_FREQUENCY_TIME_LIMIT);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_low_frequency_heap_growth",
+      (void*)JSGC_LOW_FREQUENCY_HEAP_GROWTH);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_high_frequency_large_heap_growth",
+      (void*)JSGC_HIGH_FREQUENCY_LARGE_HEAP_GROWTH);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_high_frequency_small_heap_growth",
+      (void*)JSGC_HIGH_FREQUENCY_SMALL_HEAP_GROWTH);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackBool,
+      "javascript.options.mem.gc_balanced_heap_limits",
+      (void*)JSGC_BALANCED_HEAP_LIMITS_ENABLED);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_heap_growth_factor",
+      (void*)JSGC_HEAP_GROWTH_FACTOR);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_small_heap_size_max_mb",
+      (void*)JSGC_SMALL_HEAP_SIZE_MAX);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_large_heap_size_min_mb",
+      (void*)JSGC_LARGE_HEAP_SIZE_MIN);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_allocation_threshold_mb",
+      (void*)JSGC_ALLOCATION_THRESHOLD);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_malloc_threshold_base_mb",
+      (void*)JSGC_MALLOC_THRESHOLD_BASE);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_small_heap_incremental_limit",
+      (void*)JSGC_SMALL_HEAP_INCREMENTAL_LIMIT);
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_large_heap_incremental_limit",
+      (void*)JSGC_LARGE_HEAP_INCREMENTAL_LIMIT);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_urgent_threshold_mb",
+      (void*)JSGC_URGENT_THRESHOLD_MB);
+
+  Preferences::RegisterCallbackAndCall(SetIncrementalCCPrefChangedCallback,
+                                       "dom.cycle_collector.incremental");
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_min_empty_chunk_count",
+      (void*)JSGC_MIN_EMPTY_CHUNK_COUNT);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_max_empty_chunk_count",
+      (void*)JSGC_MAX_EMPTY_CHUNK_COUNT);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_helper_thread_ratio",
+      (void*)JSGC_HELPER_THREAD_RATIO);
+
+  Preferences::RegisterCallbackAndCall(
+      SetMemoryPrefChangedCallbackInt,
+      "javascript.options.mem.gc_max_helper_threads",
+      (void*)JSGC_MAX_HELPER_THREADS);
+
+  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
+  if (!obs) {
+    MOZ_CRASH();
+  }
+
+  nsIObserver* observer = new nsJSEnvironmentObserver();
+  obs->AddObserver(observer, "memory-pressure", false);
+  obs->AddObserver(observer, "user-interaction-inactive", false);
+  obs->AddObserver(observer, "user-interaction-active", false);
+  obs->AddObserver(observer, "quit-application", false);
+  obs->AddObserver(observer, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
+  obs->AddObserver(observer, "content-child-will-shutdown", false);
+
+  sIsInitialized = true;
+}
+
+void mozilla::dom::ShutdownJSEnvironment() {
+  sShuttingDown = true;
+  sScheduler->Shutdown();
+}
+
+AsyncErrorReporter::AsyncErrorReporter(xpc::ErrorReport* aReport)
+    : Runnable("dom::AsyncErrorReporter"), mReport(aReport) {}
+
+void AsyncErrorReporter::SerializeStack(JSContext* aCx,
+                                        JS::Handle<JSObject*> aStack) {
+  mStackHolder = MakeUnique<SerializedStackHolder>();
+  mStackHolder->SerializeMainThreadOrWorkletStack(aCx, aStack);
+}
+
+void AsyncErrorReporter::SetException(JSContext* aCx,
+                                      JS::Handle<JS::Value> aException) {
+  MOZ_ASSERT(NS_IsMainThread());
+  mException.init(aCx, aException);
+  mHasException = true;
+}
+
+NS_IMETHODIMP AsyncErrorReporter::Run() {
+  AutoJSAPI jsapi;
+  // We're only using this context to deserialize a stack to report to the
+  // console, so the scope we use doesn't matter. Stack frame filtering happens
+  // based on the principal encoded into the frame and the caller compartment,
+  // not the compartment of the frame object, and the console reporting code
+  // will not be using our context, and therefore will not care what compartment
+  // it has entered.
+  DebugOnly<bool> ok = jsapi.Init(xpc::PrivilegedJunkScope());
+  MOZ_ASSERT(ok, "Problem with system global?");
+  JSContext* cx = jsapi.cx();
+  JS::Rooted<JSObject*> stack(cx);
+  JS::Rooted<JSObject*> stackGlobal(cx);
+  if (mStackHolder) {
+    stack = mStackHolder->ReadStack(cx);
+    if (stack) {
+      stackGlobal = JS::CurrentGlobalOrNull(cx);
+    }
+  }
+
+  JS::Rooted<Maybe<JS::Value>> exception(cx, Nothing());
+  if (mHasException) {
+    MOZ_ASSERT(NS_IsMainThread());
+    exception = Some(mException);
+    // Remove our reference to the exception.
+    mException.setUndefined();
+    mHasException = false;
+  }
+
+  mReport->LogToConsoleWithStack(nullptr, exception, stack, stackGlobal);
+  return NS_OK;
+}
+
+// A fast-array class for JS.  This class supports both nsIJSScriptArray and
+// nsIArray.  If it is JS itself providing and consuming this class, all work
+// can be done via nsIJSScriptArray, and avoid the conversion of elements
+// to/from nsISupports.
+// When consumed by non-JS (eg, another script language), conversion is done
+// on-the-fly.
+class nsJSArgArray final : public nsIJSArgArray {
+ public:
+  nsJSArgArray(JSContext* aContext, uint32_t argc, const JS::Value* argv,
+               nsresult* prv);
+
+  // nsISupports
+  NS_DECL_CYCLE_COLLECTING_ISUPPORTS
+  NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS_AMBIGUOUS(nsJSArgArray,
+                                                         nsIJSArgArray)
+
+  // nsIArray
+  NS_DECL_NSIARRAY
+
+  // nsIJSArgArray
+  nsresult GetArgs(uint32_t* argc, void** argv) override;
+
+  void ReleaseJSObjects();
+
+ protected:
+  ~nsJSArgArray();
+  JSContext* mContext;
+  JS::Heap<JS::Value>* mArgv;
+  uint32_t mArgc;
+};
+
+nsJSArgArray::nsJSArgArray(JSContext* aContext, uint32_t argc,
+                           const JS::Value* argv, nsresult* prv)
+    : mContext(aContext), mArgv(nullptr), mArgc(argc) {
+  // copy the array - we don't know its lifetime, and ours is tied to xpcom
+  // refcounting.
+  if (argc) {
+    mArgv = new (fallible) JS::Heap<JS::Value>[argc];
+    if (!mArgv) {
+      *prv = NS_ERROR_OUT_OF_MEMORY;
+      return;
+    }
+  }
+
+  // Callers are allowed to pass in a null argv even for argc > 0. They can
+  // then use GetArgs to initialize the values.
+  if (argv) {
+    for (uint32_t i = 0; i < argc; ++i) mArgv[i] = argv[i];
+  }
+
+  if (argc > 0) {
+    mozilla::HoldJSObjects(this);
+  }
+
+  *prv = NS_OK;
+}
+
+nsJSArgArray::~nsJSArgArray() { ReleaseJSObjects(); }
+
+void nsJSArgArray::ReleaseJSObjects() {
+  delete[] mArgv;
+
+  if (mArgc > 0) {
+    mArgc = 0;
+    mozilla::DropJSObjects(this);
+  }
+}
+
+// QueryInterface implementation for nsJSArgArray
+NS_IMPL_CYCLE_COLLECTION_CLASS(nsJSArgArray)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(nsJSArgArray)
+  tmp->ReleaseJSObjects();
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(nsJSArgArray)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(nsJSArgArray)
+  if (tmp->mArgv) {
+    for (uint32_t i = 0; i < tmp->mArgc; ++i) {
+      NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mArgv[i])
+    }
+  }
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(nsJSArgArray)
+  NS_INTERFACE_MAP_ENTRY(nsIArray)
+  NS_INTERFACE_MAP_ENTRY(nsIJSArgArray)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIJSArgArray)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(nsJSArgArray)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(nsJSArgArray)
+
+nsresult nsJSArgArray::GetArgs(uint32_t* argc, void** argv) {
+  *argv = (void*)mArgv;
+  *argc = mArgc;
+  return NS_OK;
+}
+
+// nsIArray impl
+NS_IMETHODIMP nsJSArgArray::GetLength(uint32_t* aLength) {
+  *aLength = mArgc;
+  return NS_OK;
+}
+
+NS_IMETHODIMP nsJSArgArray::QueryElementAt(uint32_t index, const nsIID& uuid,
+                                           void** result) {
+  *result = nullptr;
+  if (index >= mArgc) return NS_ERROR_INVALID_ARG;
+
+  if (uuid.Equals(NS_GET_IID(nsIVariant)) ||
+      uuid.Equals(NS_GET_IID(nsISupports))) {
+    // Have to copy a Heap into a Rooted to work with it.
+    JS::Rooted<JS::Value> val(mContext, mArgv[index]);
+    return nsContentUtils::XPConnect()->JSToVariant(mContext, val,
+                                                    (nsIVariant**)result);
+  }
+  NS_WARNING("nsJSArgArray only handles nsIVariant");
+  return NS_ERROR_NO_INTERFACE;
+}
+
+NS_IMETHODIMP nsJSArgArray::IndexOf(uint32_t startIndex, nsISupports* element,
+                                    uint32_t* _retval) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP nsJSArgArray::ScriptedEnumerate(const nsIID& aElemIID,
+                                              uint8_t aArgc,
+                                              nsISimpleEnumerator** aResult) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP nsJSArgArray::EnumerateImpl(const nsID& aEntryIID,
+                                          nsISimpleEnumerator** _retval) {
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+// The factory function
+nsresult NS_CreateJSArgv(JSContext* aContext, uint32_t argc,
+                         const JS::Value* argv, nsIJSArgArray** aArray) {
+  nsresult rv;
+  nsCOMPtr<nsIJSArgArray> ret = new nsJSArgArray(aContext, argc, argv, &rv);
+  if (NS_FAILED(rv)) {
+    return rv;
+  }
+  ret.forget(aArray);
+  return NS_OK;
+}