Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

1 files changed, 4375 insertions, 0 deletions

diff --git a/dom/bindings/BindingUtils.cpp b/dom/bindings/BindingUtils.cpp
new file mode 100644
index 0000000000..40e6a066ba
--- /dev/null
+++ b/dom/bindings/BindingUtils.cpp
@@ -0,0 +1,4375 @@
+/* -*- 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 "BindingUtils.h"
+
+#include <algorithm>
+#include <stdarg.h>
+
+#include "mozilla/Assertions.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/Encoding.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/UniquePtr.h"
+#include "mozilla/Unused.h"
+#include "mozilla/UseCounter.h"
+
+#include "AccessCheck.h"
+#include "js/CallAndConstruct.h"  // JS::Call, JS::IsCallable
+#include "js/experimental/JitInfo.h"  // JSJit{Getter,Setter,Method}CallArgs, JSJit{Getter,Setter}Op, JSJitInfo
+#include "js/friend/StackLimits.h"  // js::AutoCheckRecursionLimit
+#include "js/Id.h"
+#include "js/JSON.h"
+#include "js/MapAndSet.h"
+#include "js/Object.h"  // JS::GetClass, JS::GetCompartment, JS::GetReservedSlot, JS::SetReservedSlot
+#include "js/PropertyAndElement.h"  // JS_AlreadyHasOwnPropertyById, JS_DefineFunction, JS_DefineFunctionById, JS_DefineFunctions, JS_DefineProperties, JS_DefineProperty, JS_DefinePropertyById, JS_ForwardGetPropertyTo, JS_GetProperty, JS_HasProperty, JS_HasPropertyById
+#include "js/StableStringChars.h"
+#include "js/String.h"  // JS::GetStringLength, JS::MaxStringLength, JS::StringHasLatin1Chars
+#include "js/Symbol.h"
+#include "jsfriendapi.h"
+#include "nsContentCreatorFunctions.h"
+#include "nsContentUtils.h"
+#include "nsGlobalWindow.h"
+#include "nsHTMLTags.h"
+#include "nsIDOMGlobalPropertyInitializer.h"
+#include "nsINode.h"
+#include "nsIOService.h"
+#include "nsIPrincipal.h"
+#include "nsIXPConnect.h"
+#include "nsUTF8Utils.h"
+#include "WorkerPrivate.h"
+#include "WorkerRunnable.h"
+#include "WrapperFactory.h"
+#include "xpcprivate.h"
+#include "XrayWrapper.h"
+#include "nsPrintfCString.h"
+#include "mozilla/Sprintf.h"
+#include "nsReadableUtils.h"
+#include "nsWrapperCacheInlines.h"
+
+#include "mozilla/dom/ScriptSettings.h"
+#include "mozilla/dom/CustomElementRegistry.h"
+#include "mozilla/dom/DeprecationReportBody.h"
+#include "mozilla/dom/DOMException.h"
+#include "mozilla/dom/ElementBinding.h"
+#include "mozilla/dom/Exceptions.h"
+#include "mozilla/dom/HTMLObjectElement.h"
+#include "mozilla/dom/HTMLObjectElementBinding.h"
+#include "mozilla/dom/HTMLEmbedElement.h"
+#include "mozilla/dom/HTMLElementBinding.h"
+#include "mozilla/dom/HTMLEmbedElementBinding.h"
+#include "mozilla/dom/MaybeCrossOriginObject.h"
+#include "mozilla/dom/ObservableArrayProxyHandler.h"
+#include "mozilla/dom/ReportingUtils.h"
+#include "mozilla/dom/XULElementBinding.h"
+#include "mozilla/dom/XULFrameElementBinding.h"
+#include "mozilla/dom/XULMenuElementBinding.h"
+#include "mozilla/dom/XULPopupElementBinding.h"
+#include "mozilla/dom/XULResizerElementBinding.h"
+#include "mozilla/dom/XULTextElementBinding.h"
+#include "mozilla/dom/XULTreeElementBinding.h"
+#include "mozilla/dom/Promise.h"
+#include "mozilla/dom/WebIDLGlobalNameHash.h"
+#include "mozilla/dom/WorkerPrivate.h"
+#include "mozilla/dom/WorkerScope.h"
+#include "mozilla/dom/XrayExpandoClass.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "ipc/ErrorIPCUtils.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
+#include "mozilla/dom/DocGroup.h"
+#include "nsXULElement.h"
+
+namespace mozilla {
+namespace dom {
+
+// Forward declare GetConstructorObject methods.
+#define HTML_TAG(_tag, _classname, _interfacename)  \
+  namespace HTML##_interfacename##Element_Binding { \
+    JSObject* GetConstructorObject(JSContext*);     \
+  }
+#define HTML_OTHER(_tag)
+#include "nsHTMLTagList.h"
+#undef HTML_TAG
+#undef HTML_OTHER
+
+using constructorGetterCallback = JSObject* (*)(JSContext*);
+
+// Mapping of html tag and GetConstructorObject methods.
+#define HTML_TAG(_tag, _classname, _interfacename) \
+  HTML##_interfacename##Element_Binding::GetConstructorObject,
+#define HTML_OTHER(_tag) nullptr,
+// We use eHTMLTag_foo (where foo is the tag) which is defined in nsHTMLTags.h
+// to index into this array.
+static const constructorGetterCallback sConstructorGetterCallback[] = {
+    HTMLUnknownElement_Binding::GetConstructorObject,
+#include "nsHTMLTagList.h"
+#undef HTML_TAG
+#undef HTML_OTHER
+};
+
+static const JSErrorFormatString ErrorFormatString[] = {
+#define MSG_DEF(_name, _argc, _has_context, _exn, _str) \
+  {#_name, _str, _argc, _exn},
+#include "mozilla/dom/Errors.msg"
+#undef MSG_DEF
+};
+
+#define MSG_DEF(_name, _argc, _has_context, _exn, _str) \
+  static_assert(                                        \
+      (_argc) < JS::MaxNumErrorArguments, #_name        \
+      " must only have as many error arguments as the JS engine can support");
+#include "mozilla/dom/Errors.msg"
+#undef MSG_DEF
+
+static const JSErrorFormatString* GetErrorMessage(void* aUserRef,
+                                                  const unsigned aErrorNumber) {
+  MOZ_ASSERT(aErrorNumber < ArrayLength(ErrorFormatString));
+  return &ErrorFormatString[aErrorNumber];
+}
+
+uint16_t GetErrorArgCount(const ErrNum aErrorNumber) {
+  return GetErrorMessage(nullptr, aErrorNumber)->argCount;
+}
+
+// aErrorNumber needs to be unsigned, not an ErrNum, because the latter makes
+// va_start have undefined behavior, and we do not want undefined behavior.
+void binding_detail::ThrowErrorMessage(JSContext* aCx,
+                                       const unsigned aErrorNumber, ...) {
+  va_list ap;
+  va_start(ap, aErrorNumber);
+
+  if (!ErrorFormatHasContext[aErrorNumber]) {
+    JS_ReportErrorNumberUTF8VA(aCx, GetErrorMessage, nullptr, aErrorNumber, ap);
+    va_end(ap);
+    return;
+  }
+
+  // Our first arg is the context arg.  We want to replace nullptr with empty
+  // string, leave empty string alone, and for anything else append ": " to the
+  // end.  See also the behavior of
+  // TErrorResult::SetPendingExceptionWithMessage, which this is mirroring for
+  // exceptions that are thrown directly, not via an ErrorResult.
+  const char* args[JS::MaxNumErrorArguments + 1];
+  size_t argCount = GetErrorArgCount(static_cast<ErrNum>(aErrorNumber));
+  MOZ_ASSERT(argCount > 0, "We have a context arg!");
+  nsAutoCString firstArg;
+
+  for (size_t i = 0; i < argCount; ++i) {
+    args[i] = va_arg(ap, const char*);
+    if (i == 0) {
+      if (args[0] && *args[0]) {
+        firstArg.Append(args[0]);
+        firstArg.AppendLiteral(": ");
+      }
+      args[0] = firstArg.get();
+    }
+  }
+
+  JS_ReportErrorNumberUTF8Array(aCx, GetErrorMessage, nullptr, aErrorNumber,
+                                args);
+  va_end(ap);
+}
+
+static bool ThrowInvalidThis(JSContext* aCx, const JS::CallArgs& aArgs,
+                             bool aSecurityError, const char* aInterfaceName) {
+  NS_ConvertASCIItoUTF16 ifaceName(aInterfaceName);
+  // This should only be called for DOM methods/getters/setters, which
+  // are JSNative-backed functions, so we can assume that
+  // JS_ValueToFunction and JS_GetFunctionDisplayId will both return
+  // non-null and that JS_GetStringCharsZ returns non-null.
+  JS::Rooted<JSFunction*> func(aCx, JS_ValueToFunction(aCx, aArgs.calleev()));
+  MOZ_ASSERT(func);
+  JS::Rooted<JSString*> funcName(aCx, JS_GetFunctionDisplayId(func));
+  MOZ_ASSERT(funcName);
+  nsAutoJSString funcNameStr;
+  if (!funcNameStr.init(aCx, funcName)) {
+    return false;
+  }
+  if (aSecurityError) {
+    return Throw(aCx, NS_ERROR_DOM_SECURITY_ERR,
+                 nsPrintfCString("Permission to call '%s' denied.",
+                                 NS_ConvertUTF16toUTF8(funcNameStr).get()));
+  }
+
+  const ErrNum errorNumber = MSG_METHOD_THIS_DOES_NOT_IMPLEMENT_INTERFACE;
+  MOZ_RELEASE_ASSERT(GetErrorArgCount(errorNumber) == 2);
+  JS_ReportErrorNumberUC(aCx, GetErrorMessage, nullptr,
+                         static_cast<unsigned>(errorNumber),
+                         static_cast<const char16_t*>(funcNameStr.get()),
+                         static_cast<const char16_t*>(ifaceName.get()));
+  return false;
+}
+
+bool ThrowInvalidThis(JSContext* aCx, const JS::CallArgs& aArgs,
+                      bool aSecurityError, prototypes::ID aProtoId) {
+  return ThrowInvalidThis(aCx, aArgs, aSecurityError,
+                          NamesOfInterfacesWithProtos(aProtoId));
+}
+
+bool ThrowNoSetterArg(JSContext* aCx, const JS::CallArgs& aArgs,
+                      prototypes::ID aProtoId) {
+  nsPrintfCString errorMessage("%s attribute setter",
+                               NamesOfInterfacesWithProtos(aProtoId));
+  return aArgs.requireAtLeast(aCx, errorMessage.get(), 1);
+}
+
+}  // namespace dom
+
+namespace binding_danger {
+
+template <typename CleanupPolicy>
+struct TErrorResult<CleanupPolicy>::Message {
+  Message() : mErrorNumber(dom::Err_Limit) {
+    MOZ_COUNT_CTOR(TErrorResult::Message);
+  }
+  ~Message() { MOZ_COUNT_DTOR(TErrorResult::Message); }
+
+  // UTF-8 strings (probably ASCII in most cases) in mArgs.
+  nsTArray<nsCString> mArgs;
+  dom::ErrNum mErrorNumber;
+
+  bool HasCorrectNumberOfArguments() {
+    return GetErrorArgCount(mErrorNumber) == mArgs.Length();
+  }
+
+  bool operator==(const TErrorResult<CleanupPolicy>::Message& aRight) const {
+    return mErrorNumber == aRight.mErrorNumber && mArgs == aRight.mArgs;
+  }
+};
+
+template <typename CleanupPolicy>
+nsTArray<nsCString>& TErrorResult<CleanupPolicy>::CreateErrorMessageHelper(
+    const dom::ErrNum errorNumber, nsresult errorType) {
+  AssertInOwningThread();
+  mResult = errorType;
+
+  Message* message = InitMessage(new Message());
+  message->mErrorNumber = errorNumber;
+  return message->mArgs;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SerializeMessage(
+    IPC::MessageWriter* aWriter) const {
+  using namespace IPC;
+  AssertInOwningThread();
+  MOZ_ASSERT(mUnionState == HasMessage);
+  MOZ_ASSERT(mExtra.mMessage);
+  WriteParam(aWriter, mExtra.mMessage->mArgs);
+  WriteParam(aWriter, mExtra.mMessage->mErrorNumber);
+}
+
+template <typename CleanupPolicy>
+bool TErrorResult<CleanupPolicy>::DeserializeMessage(
+    IPC::MessageReader* aReader) {
+  using namespace IPC;
+  AssertInOwningThread();
+  auto readMessage = MakeUnique<Message>();
+  if (!ReadParam(aReader, &readMessage->mArgs) ||
+      !ReadParam(aReader, &readMessage->mErrorNumber)) {
+    return false;
+  }
+  if (!readMessage->HasCorrectNumberOfArguments()) {
+    return false;
+  }
+
+  MOZ_ASSERT(mUnionState == HasNothing);
+  InitMessage(readMessage.release());
+#ifdef DEBUG
+  mUnionState = HasMessage;
+#endif  // DEBUG
+  return true;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SetPendingExceptionWithMessage(
+    JSContext* aCx, const char* context) {
+  AssertInOwningThread();
+  MOZ_ASSERT(mUnionState == HasMessage);
+  MOZ_ASSERT(mExtra.mMessage,
+             "SetPendingExceptionWithMessage() can be called only once");
+
+  Message* message = mExtra.mMessage;
+  MOZ_RELEASE_ASSERT(message->HasCorrectNumberOfArguments());
+  if (dom::ErrorFormatHasContext[message->mErrorNumber]) {
+    MOZ_ASSERT(!message->mArgs.IsEmpty(), "How could we have no args here?");
+    MOZ_ASSERT(message->mArgs[0].IsEmpty(), "Context should not be set yet!");
+    if (context) {
+      // Prepend our context and ": "; see API documentation.
+      message->mArgs[0].AssignASCII(context);
+      message->mArgs[0].AppendLiteral(": ");
+    }
+  }
+  const uint32_t argCount = message->mArgs.Length();
+  const char* args[JS::MaxNumErrorArguments + 1];
+  for (uint32_t i = 0; i < argCount; ++i) {
+    args[i] = message->mArgs.ElementAt(i).get();
+  }
+  args[argCount] = nullptr;
+
+  JS_ReportErrorNumberUTF8Array(aCx, dom::GetErrorMessage, nullptr,
+                                static_cast<unsigned>(message->mErrorNumber),
+                                argCount > 0 ? args : nullptr);
+
+  ClearMessage();
+  mResult = NS_OK;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::ClearMessage() {
+  AssertInOwningThread();
+  MOZ_ASSERT(IsErrorWithMessage());
+  MOZ_ASSERT(mUnionState == HasMessage);
+  delete mExtra.mMessage;
+  mExtra.mMessage = nullptr;
+#ifdef DEBUG
+  mUnionState = HasNothing;
+#endif  // DEBUG
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::ThrowJSException(JSContext* cx,
+                                                   JS::Handle<JS::Value> exn) {
+  AssertInOwningThread();
+  MOZ_ASSERT(mMightHaveUnreportedJSException,
+             "Why didn't you tell us you planned to throw a JS exception?");
+
+  ClearUnionData();
+
+  // Make sure mExtra.mJSException is initialized _before_ we try to root it.
+  // But don't set it to exn yet, because we don't want to do that until after
+  // we root.
+  JS::Value& exc = InitJSException();
+  if (!js::AddRawValueRoot(cx, &exc, "TErrorResult::mExtra::mJSException")) {
+    // Don't use NS_ERROR_INTERNAL_ERRORRESULT_JS_EXCEPTION, because that
+    // indicates we have in fact rooted mExtra.mJSException.
+    mResult = NS_ERROR_OUT_OF_MEMORY;
+  } else {
+    exc = exn;
+    mResult = NS_ERROR_INTERNAL_ERRORRESULT_JS_EXCEPTION;
+#ifdef DEBUG
+    mUnionState = HasJSException;
+#endif  // DEBUG
+  }
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SetPendingJSException(JSContext* cx) {
+  AssertInOwningThread();
+  MOZ_ASSERT(!mMightHaveUnreportedJSException,
+             "Why didn't you tell us you planned to handle JS exceptions?");
+  MOZ_ASSERT(mUnionState == HasJSException);
+
+  JS::Rooted<JS::Value> exception(cx, mExtra.mJSException);
+  if (JS_WrapValue(cx, &exception)) {
+    JS_SetPendingException(cx, exception);
+  }
+  mExtra.mJSException = exception;
+  // If JS_WrapValue failed, not much we can do about it...  No matter
+  // what, go ahead and unroot mExtra.mJSException.
+  js::RemoveRawValueRoot(cx, &mExtra.mJSException);
+
+  mResult = NS_OK;
+#ifdef DEBUG
+  mUnionState = HasNothing;
+#endif  // DEBUG
+}
+
+template <typename CleanupPolicy>
+struct TErrorResult<CleanupPolicy>::DOMExceptionInfo {
+  DOMExceptionInfo(nsresult rv, const nsACString& message)
+      : mMessage(message), mRv(rv) {}
+
+  nsCString mMessage;
+  nsresult mRv;
+
+  bool operator==(
+      const TErrorResult<CleanupPolicy>::DOMExceptionInfo& aRight) const {
+    return mRv == aRight.mRv && mMessage == aRight.mMessage;
+  }
+};
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SerializeDOMExceptionInfo(
+    IPC::MessageWriter* aWriter) const {
+  using namespace IPC;
+  AssertInOwningThread();
+  MOZ_ASSERT(mUnionState == HasDOMExceptionInfo);
+  MOZ_ASSERT(mExtra.mDOMExceptionInfo);
+  WriteParam(aWriter, mExtra.mDOMExceptionInfo->mMessage);
+  WriteParam(aWriter, mExtra.mDOMExceptionInfo->mRv);
+}
+
+template <typename CleanupPolicy>
+bool TErrorResult<CleanupPolicy>::DeserializeDOMExceptionInfo(
+    IPC::MessageReader* aReader) {
+  using namespace IPC;
+  AssertInOwningThread();
+  nsCString message;
+  nsresult rv;
+  if (!ReadParam(aReader, &message) || !ReadParam(aReader, &rv)) {
+    return false;
+  }
+
+  MOZ_ASSERT(mUnionState == HasNothing);
+  MOZ_ASSERT(IsDOMException());
+  InitDOMExceptionInfo(new DOMExceptionInfo(rv, message));
+#ifdef DEBUG
+  mUnionState = HasDOMExceptionInfo;
+#endif  // DEBUG
+  return true;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::ThrowDOMException(nsresult rv,
+                                                    const nsACString& message) {
+  AssertInOwningThread();
+  ClearUnionData();
+
+  mResult = NS_ERROR_INTERNAL_ERRORRESULT_DOMEXCEPTION;
+  InitDOMExceptionInfo(new DOMExceptionInfo(rv, message));
+#ifdef DEBUG
+  mUnionState = HasDOMExceptionInfo;
+#endif
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SetPendingDOMException(JSContext* cx,
+                                                         const char* context) {
+  AssertInOwningThread();
+  MOZ_ASSERT(mUnionState == HasDOMExceptionInfo);
+  MOZ_ASSERT(mExtra.mDOMExceptionInfo,
+             "SetPendingDOMException() can be called only once");
+
+  if (context && !mExtra.mDOMExceptionInfo->mMessage.IsEmpty()) {
+    // Prepend our context and ": "; see API documentation.
+    nsAutoCString prefix(context);
+    prefix.AppendLiteral(": ");
+    mExtra.mDOMExceptionInfo->mMessage.Insert(prefix, 0);
+  }
+
+  dom::Throw(cx, mExtra.mDOMExceptionInfo->mRv,
+             mExtra.mDOMExceptionInfo->mMessage);
+
+  ClearDOMExceptionInfo();
+  mResult = NS_OK;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::ClearDOMExceptionInfo() {
+  AssertInOwningThread();
+  MOZ_ASSERT(IsDOMException());
+  MOZ_ASSERT(mUnionState == HasDOMExceptionInfo);
+  delete mExtra.mDOMExceptionInfo;
+  mExtra.mDOMExceptionInfo = nullptr;
+#ifdef DEBUG
+  mUnionState = HasNothing;
+#endif  // DEBUG
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::ClearUnionData() {
+  AssertInOwningThread();
+  if (IsJSException()) {
+    JSContext* cx = dom::danger::GetJSContext();
+    MOZ_ASSERT(cx);
+    mExtra.mJSException.setUndefined();
+    js::RemoveRawValueRoot(cx, &mExtra.mJSException);
+#ifdef DEBUG
+    mUnionState = HasNothing;
+#endif  // DEBUG
+  } else if (IsErrorWithMessage()) {
+    ClearMessage();
+  } else if (IsDOMException()) {
+    ClearDOMExceptionInfo();
+  }
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SetPendingGenericErrorException(
+    JSContext* cx) {
+  AssertInOwningThread();
+  MOZ_ASSERT(!IsErrorWithMessage());
+  MOZ_ASSERT(!IsJSException());
+  MOZ_ASSERT(!IsDOMException());
+  dom::Throw(cx, ErrorCode());
+  mResult = NS_OK;
+}
+
+template <typename CleanupPolicy>
+TErrorResult<CleanupPolicy>& TErrorResult<CleanupPolicy>::operator=(
+    TErrorResult<CleanupPolicy>&& aRHS) {
+  AssertInOwningThread();
+  aRHS.AssertInOwningThread();
+  // Clear out any union members we may have right now, before we
+  // start writing to it.
+  ClearUnionData();
+
+#ifdef DEBUG
+  mMightHaveUnreportedJSException = aRHS.mMightHaveUnreportedJSException;
+  aRHS.mMightHaveUnreportedJSException = false;
+#endif
+  if (aRHS.IsErrorWithMessage()) {
+    InitMessage(aRHS.mExtra.mMessage);
+    aRHS.mExtra.mMessage = nullptr;
+  } else if (aRHS.IsJSException()) {
+    JSContext* cx = dom::danger::GetJSContext();
+    MOZ_ASSERT(cx);
+    JS::Value& exn = InitJSException();
+    if (!js::AddRawValueRoot(cx, &exn, "TErrorResult::mExtra::mJSException")) {
+      MOZ_CRASH("Could not root mExtra.mJSException, we're about to OOM");
+    }
+    mExtra.mJSException = aRHS.mExtra.mJSException;
+    aRHS.mExtra.mJSException.setUndefined();
+    js::RemoveRawValueRoot(cx, &aRHS.mExtra.mJSException);
+  } else if (aRHS.IsDOMException()) {
+    InitDOMExceptionInfo(aRHS.mExtra.mDOMExceptionInfo);
+    aRHS.mExtra.mDOMExceptionInfo = nullptr;
+  } else {
+    // Null out the union on both sides for hygiene purposes.  This is purely
+    // precautionary, so InitMessage/placement-new is unnecessary.
+    mExtra.mMessage = aRHS.mExtra.mMessage = nullptr;
+  }
+
+#ifdef DEBUG
+  mUnionState = aRHS.mUnionState;
+  aRHS.mUnionState = HasNothing;
+#endif  // DEBUG
+
+  // Note: It's important to do this last, since this affects the condition
+  // checks above!
+  mResult = aRHS.mResult;
+  aRHS.mResult = NS_OK;
+  return *this;
+}
+
+template <typename CleanupPolicy>
+bool TErrorResult<CleanupPolicy>::operator==(const ErrorResult& aRight) const {
+  auto right = reinterpret_cast<const TErrorResult<CleanupPolicy>*>(&aRight);
+
+  if (mResult != right->mResult) {
+    return false;
+  }
+
+  if (IsJSException()) {
+    // js exceptions are always non-equal
+    return false;
+  }
+
+  if (IsErrorWithMessage()) {
+    return *mExtra.mMessage == *right->mExtra.mMessage;
+  }
+
+  if (IsDOMException()) {
+    return *mExtra.mDOMExceptionInfo == *right->mExtra.mDOMExceptionInfo;
+  }
+
+  return true;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::CloneTo(TErrorResult& aRv) const {
+  AssertInOwningThread();
+  aRv.AssertInOwningThread();
+  aRv.ClearUnionData();
+  aRv.mResult = mResult;
+#ifdef DEBUG
+  aRv.mMightHaveUnreportedJSException = mMightHaveUnreportedJSException;
+#endif
+
+  if (IsErrorWithMessage()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasMessage;
+#endif
+    Message* message = aRv.InitMessage(new Message());
+    message->mArgs = mExtra.mMessage->mArgs.Clone();
+    message->mErrorNumber = mExtra.mMessage->mErrorNumber;
+  } else if (IsDOMException()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasDOMExceptionInfo;
+#endif
+    auto* exnInfo = new DOMExceptionInfo(mExtra.mDOMExceptionInfo->mRv,
+                                         mExtra.mDOMExceptionInfo->mMessage);
+    aRv.InitDOMExceptionInfo(exnInfo);
+  } else if (IsJSException()) {
+#ifdef DEBUG
+    aRv.mUnionState = HasJSException;
+#endif
+    JSContext* cx = dom::danger::GetJSContext();
+    JS::Rooted<JS::Value> exception(cx, mExtra.mJSException);
+    aRv.ThrowJSException(cx, exception);
+  }
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SuppressException() {
+  AssertInOwningThread();
+  WouldReportJSException();
+  ClearUnionData();
+  // We don't use AssignErrorCode, because we want to override existing error
+  // states, which AssignErrorCode is not allowed to do.
+  mResult = NS_OK;
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::SetPendingException(JSContext* cx,
+                                                      const char* context) {
+  AssertInOwningThread();
+  if (IsUncatchableException()) {
+    // Nuke any existing exception on cx, to make sure we're uncatchable.
+    JS_ClearPendingException(cx);
+    // Don't do any reporting.  Just return, to create an
+    // uncatchable exception.
+    mResult = NS_OK;
+    return;
+  }
+  if (IsJSContextException()) {
+    // Whatever we need to throw is on the JSContext already.
+    MOZ_ASSERT(JS_IsExceptionPending(cx));
+    mResult = NS_OK;
+    return;
+  }
+  if (IsErrorWithMessage()) {
+    SetPendingExceptionWithMessage(cx, context);
+    return;
+  }
+  if (IsJSException()) {
+    SetPendingJSException(cx);
+    return;
+  }
+  if (IsDOMException()) {
+    SetPendingDOMException(cx, context);
+    return;
+  }
+  SetPendingGenericErrorException(cx);
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::StealExceptionFromJSContext(JSContext* cx) {
+  AssertInOwningThread();
+  MOZ_ASSERT(mMightHaveUnreportedJSException,
+             "Why didn't you tell us you planned to throw a JS exception?");
+
+  JS::Rooted<JS::Value> exn(cx);
+  if (!JS_GetPendingException(cx, &exn)) {
+    ThrowUncatchableException();
+    return;
+  }
+
+  ThrowJSException(cx, exn);
+  JS_ClearPendingException(cx);
+}
+
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::NoteJSContextException(JSContext* aCx) {
+  AssertInOwningThread();
+  if (JS_IsExceptionPending(aCx)) {
+    mResult = NS_ERROR_INTERNAL_ERRORRESULT_EXCEPTION_ON_JSCONTEXT;
+  } else {
+    mResult = NS_ERROR_UNCATCHABLE_EXCEPTION;
+  }
+}
+
+/* static */
+template <typename CleanupPolicy>
+void TErrorResult<CleanupPolicy>::EnsureUTF8Validity(nsCString& aValue,
+                                                     size_t aValidUpTo) {
+  nsCString valid;
+  if (NS_SUCCEEDED(UTF_8_ENCODING->DecodeWithoutBOMHandling(aValue, valid,
+                                                            aValidUpTo))) {
+    aValue = valid;
+  } else {
+    aValue.SetLength(aValidUpTo);
+  }
+}
+
+template class TErrorResult<JustAssertCleanupPolicy>;
+template class TErrorResult<AssertAndSuppressCleanupPolicy>;
+template class TErrorResult<JustSuppressCleanupPolicy>;
+template class TErrorResult<ThreadSafeJustSuppressCleanupPolicy>;
+
+}  // namespace binding_danger
+
+namespace dom {
+
+bool DefineConstants(JSContext* cx, JS::Handle<JSObject*> obj,
+                     const ConstantSpec* cs) {
+  JS::Rooted<JS::Value> value(cx);
+  for (; cs->name; ++cs) {
+    value = cs->value;
+    bool ok = JS_DefineProperty(
+        cx, obj, cs->name, value,
+        JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT);
+    if (!ok) {
+      return false;
+    }
+  }
+  return true;
+}
+
+static inline bool Define(JSContext* cx, JS::Handle<JSObject*> obj,
+                          const JSFunctionSpec* spec) {
+  return JS_DefineFunctions(cx, obj, spec);
+}
+static inline bool Define(JSContext* cx, JS::Handle<JSObject*> obj,
+                          const JSPropertySpec* spec) {
+  return JS_DefineProperties(cx, obj, spec);
+}
+static inline bool Define(JSContext* cx, JS::Handle<JSObject*> obj,
+                          const ConstantSpec* spec) {
+  return DefineConstants(cx, obj, spec);
+}
+
+template <typename T>
+bool DefinePrefable(JSContext* cx, JS::Handle<JSObject*> obj,
+                    const Prefable<T>* props) {
+  MOZ_ASSERT(props);
+  MOZ_ASSERT(props->specs);
+  do {
+    // Define if enabled
+    if (props->isEnabled(cx, obj)) {
+      if (!Define(cx, obj, props->specs)) {
+        return false;
+      }
+    }
+  } while ((++props)->specs);
+  return true;
+}
+
+bool DefineLegacyUnforgeableMethods(
+    JSContext* cx, JS::Handle<JSObject*> obj,
+    const Prefable<const JSFunctionSpec>* props) {
+  return DefinePrefable(cx, obj, props);
+}
+
+bool DefineLegacyUnforgeableAttributes(
+    JSContext* cx, JS::Handle<JSObject*> obj,
+    const Prefable<const JSPropertySpec>* props) {
+  return DefinePrefable(cx, obj, props);
+}
+
+// We should use JSFunction objects for interface objects, but we need a custom
+// hasInstance hook because we have new interface objects on prototype chains of
+// old (XPConnect-based) bindings. We also need Xrays and arbitrary numbers of
+// reserved slots (e.g. for named constructors).  So we define a custom
+// funToString ObjectOps member for interface objects.
+JSString* InterfaceObjectToString(JSContext* aCx, JS::Handle<JSObject*> aObject,
+                                  bool /* isToSource */) {
+  const JSClass* clasp = JS::GetClass(aObject);
+  MOZ_ASSERT(IsDOMIfaceAndProtoClass(clasp));
+
+  const DOMIfaceAndProtoJSClass* ifaceAndProtoJSClass =
+      DOMIfaceAndProtoJSClass::FromJSClass(clasp);
+  return JS_NewStringCopyZ(aCx, ifaceAndProtoJSClass->mFunToString);
+}
+
+bool Constructor(JSContext* cx, unsigned argc, JS::Value* vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  const JS::Value& v = js::GetFunctionNativeReserved(
+      &args.callee(), CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT);
+  const JSNativeHolder* nativeHolder =
+      static_cast<const JSNativeHolder*>(v.toPrivate());
+  return (nativeHolder->mNative)(cx, argc, vp);
+}
+
+static JSObject* CreateConstructor(JSContext* cx, JS::Handle<JSObject*> global,
+                                   const char* name,
+                                   const JSNativeHolder* nativeHolder,
+                                   unsigned ctorNargs) {
+  JSFunction* fun = js::NewFunctionWithReserved(cx, Constructor, ctorNargs,
+                                                JSFUN_CONSTRUCTOR, name);
+  if (!fun) {
+    return nullptr;
+  }
+
+  JSObject* constructor = JS_GetFunctionObject(fun);
+  js::SetFunctionNativeReserved(
+      constructor, CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT,
+      JS::PrivateValue(const_cast<JSNativeHolder*>(nativeHolder)));
+  return constructor;
+}
+
+static bool DefineConstructor(JSContext* cx, JS::Handle<JSObject*> global,
+                              JS::Handle<jsid> name,
+                              JS::Handle<JSObject*> constructor) {
+  bool alreadyDefined;
+  if (!JS_AlreadyHasOwnPropertyById(cx, global, name, &alreadyDefined)) {
+    return false;
+  }
+
+  // This is Enumerable: False per spec.
+  return alreadyDefined ||
+         JS_DefinePropertyById(cx, global, name, constructor, JSPROP_RESOLVING);
+}
+
+static bool DefineConstructor(JSContext* cx, JS::Handle<JSObject*> global,
+                              const char* name,
+                              JS::Handle<JSObject*> constructor) {
+  JSString* nameStr = JS_AtomizeString(cx, name);
+  if (!nameStr) {
+    return false;
+  }
+  JS::Rooted<JS::PropertyKey> nameKey(cx, JS::PropertyKey::NonIntAtom(nameStr));
+  return DefineConstructor(cx, global, nameKey, constructor);
+}
+
+static bool DefineToStringTag(JSContext* cx, JS::Handle<JSObject*> obj,
+                              JS::Handle<JSString*> class_name) {
+  JS::Rooted<jsid> toStringTagId(
+      cx, JS::GetWellKnownSymbolKey(cx, JS::SymbolCode::toStringTag));
+  return JS_DefinePropertyById(cx, obj, toStringTagId, class_name,
+                               JSPROP_READONLY);
+}
+
+// name must be an atom (or JS::PropertyKey::NonIntAtom will assert).
+static JSObject* CreateInterfaceObject(
+    JSContext* cx, JS::Handle<JSObject*> global,
+    JS::Handle<JSObject*> constructorProto, const JSClass* constructorClass,
+    unsigned ctorNargs, const LegacyFactoryFunction* namedConstructors,
+    JS::Handle<JSObject*> proto, const NativeProperties* properties,
+    const NativeProperties* chromeOnlyProperties, JS::Handle<JSString*> name,
+    bool isChrome, bool defineOnGlobal, const char* const* legacyWindowAliases,
+    bool isNamespace) {
+  JS::Rooted<JSObject*> constructor(cx);
+  MOZ_ASSERT(constructorProto);
+  MOZ_ASSERT(constructorClass);
+  constructor =
+      JS_NewObjectWithGivenProto(cx, constructorClass, constructorProto);
+  if (!constructor) {
+    return nullptr;
+  }
+
+  if (!isNamespace) {
+    if (!JS_DefineProperty(cx, constructor, "length", ctorNargs,
+                           JSPROP_READONLY)) {
+      return nullptr;
+    }
+
+    if (!JS_DefineProperty(cx, constructor, "name", name, JSPROP_READONLY)) {
+      return nullptr;
+    }
+  }
+
+  if (DOMIfaceAndProtoJSClass::FromJSClass(constructorClass)
+          ->wantsInterfaceHasInstance) {
+    if (StaticPrefs::dom_webidl_crosscontext_hasinstance_enabled()) {
+      JS::Rooted<jsid> hasInstanceId(
+          cx, JS::GetWellKnownSymbolKey(cx, JS::SymbolCode::hasInstance));
+      if (!JS_DefineFunctionById(
+              cx, constructor, hasInstanceId, InterfaceHasInstance, 1,
+              // Flags match those of Function[Symbol.hasInstance]
+              JSPROP_READONLY | JSPROP_PERMANENT)) {
+        return nullptr;
+      }
+    }
+
+    if (isChrome && !JS_DefineFunction(cx, constructor, "isInstance",
+                                       InterfaceIsInstance, 1,
+                                       // Don't bother making it enumerable
+                                       0)) {
+      return nullptr;
+    }
+  }
+
+  if (properties) {
+    if (properties->HasStaticMethods() &&
+        !DefinePrefable(cx, constructor, properties->StaticMethods())) {
+      return nullptr;
+    }
+
+    if (properties->HasStaticAttributes() &&
+        !DefinePrefable(cx, constructor, properties->StaticAttributes())) {
+      return nullptr;
+    }
+
+    if (properties->HasConstants() &&
+        !DefinePrefable(cx, constructor, properties->Constants())) {
+      return nullptr;
+    }
+  }
+
+  if (chromeOnlyProperties && isChrome) {
+    if (chromeOnlyProperties->HasStaticMethods() &&
+        !DefinePrefable(cx, constructor,
+                        chromeOnlyProperties->StaticMethods())) {
+      return nullptr;
+    }
+
+    if (chromeOnlyProperties->HasStaticAttributes() &&
+        !DefinePrefable(cx, constructor,
+                        chromeOnlyProperties->StaticAttributes())) {
+      return nullptr;
+    }
+
+    if (chromeOnlyProperties->HasConstants() &&
+        !DefinePrefable(cx, constructor, chromeOnlyProperties->Constants())) {
+      return nullptr;
+    }
+  }
+
+  if (isNamespace && !DefineToStringTag(cx, constructor, name)) {
+    return nullptr;
+  }
+
+  if (proto && !JS_LinkConstructorAndPrototype(cx, constructor, proto)) {
+    return nullptr;
+  }
+
+  JS::Rooted<jsid> nameStr(cx, JS::PropertyKey::NonIntAtom(name));
+  if (defineOnGlobal && !DefineConstructor(cx, global, nameStr, constructor)) {
+    return nullptr;
+  }
+
+  if (legacyWindowAliases && NS_IsMainThread()) {
+    for (; *legacyWindowAliases; ++legacyWindowAliases) {
+      if (!DefineConstructor(cx, global, *legacyWindowAliases, constructor)) {
+        return nullptr;
+      }
+    }
+  }
+
+  if (namedConstructors) {
+    int namedConstructorSlot = DOM_INTERFACE_SLOTS_BASE;
+    while (namedConstructors->mName) {
+      JS::Rooted<JSObject*> namedConstructor(
+          cx, CreateConstructor(cx, global, namedConstructors->mName,
+                                &namedConstructors->mHolder,
+                                namedConstructors->mNargs));
+      if (!namedConstructor ||
+          !JS_DefineProperty(cx, namedConstructor, "prototype", proto,
+                             JSPROP_PERMANENT | JSPROP_READONLY) ||
+          (defineOnGlobal &&
+           !DefineConstructor(cx, global, namedConstructors->mName,
+                              namedConstructor))) {
+        return nullptr;
+      }
+      JS::SetReservedSlot(constructor, namedConstructorSlot++,
+                          JS::ObjectValue(*namedConstructor));
+      ++namedConstructors;
+    }
+  }
+
+  return constructor;
+}
+
+static JSObject* CreateInterfacePrototypeObject(
+    JSContext* cx, JS::Handle<JSObject*> global,
+    JS::Handle<JSObject*> parentProto, const JSClass* protoClass,
+    const NativeProperties* properties,
+    const NativeProperties* chromeOnlyProperties,
+    const char* const* unscopableNames, JS::Handle<JSString*> name,
+    bool isGlobal) {
+  JS::Rooted<JSObject*> ourProto(
+      cx, JS_NewObjectWithGivenProto(cx, protoClass, parentProto));
+  if (!ourProto ||
+      // We don't try to define properties on the global's prototype; those
+      // properties go on the global itself.
+      (!isGlobal &&
+       !DefineProperties(cx, ourProto, properties, chromeOnlyProperties))) {
+    return nullptr;
+  }
+
+  if (unscopableNames) {
+    JS::Rooted<JSObject*> unscopableObj(
+        cx, JS_NewObjectWithGivenProto(cx, nullptr, nullptr));
+    if (!unscopableObj) {
+      return nullptr;
+    }
+
+    for (; *unscopableNames; ++unscopableNames) {
+      if (!JS_DefineProperty(cx, unscopableObj, *unscopableNames,
+                             JS::TrueHandleValue, JSPROP_ENUMERATE)) {
+        return nullptr;
+      }
+    }
+
+    JS::Rooted<jsid> unscopableId(
+        cx, JS::GetWellKnownSymbolKey(cx, JS::SymbolCode::unscopables));
+    // Readonly and non-enumerable to match Array.prototype.
+    if (!JS_DefinePropertyById(cx, ourProto, unscopableId, unscopableObj,
+                               JSPROP_READONLY)) {
+      return nullptr;
+    }
+  }
+
+  if (!DefineToStringTag(cx, ourProto, name)) {
+    return nullptr;
+  }
+
+  return ourProto;
+}
+
+bool DefineProperties(JSContext* cx, JS::Handle<JSObject*> obj,
+                      const NativeProperties* properties,
+                      const NativeProperties* chromeOnlyProperties) {
+  if (properties) {
+    if (properties->HasMethods() &&
+        !DefinePrefable(cx, obj, properties->Methods())) {
+      return false;
+    }
+
+    if (properties->HasAttributes() &&
+        !DefinePrefable(cx, obj, properties->Attributes())) {
+      return false;
+    }
+
+    if (properties->HasConstants() &&
+        !DefinePrefable(cx, obj, properties->Constants())) {
+      return false;
+    }
+  }
+
+  if (chromeOnlyProperties) {
+    if (chromeOnlyProperties->HasMethods() &&
+        !DefinePrefable(cx, obj, chromeOnlyProperties->Methods())) {
+      return false;
+    }
+
+    if (chromeOnlyProperties->HasAttributes() &&
+        !DefinePrefable(cx, obj, chromeOnlyProperties->Attributes())) {
+      return false;
+    }
+
+    if (chromeOnlyProperties->HasConstants() &&
+        !DefinePrefable(cx, obj, chromeOnlyProperties->Constants())) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+void CreateInterfaceObjects(
+    JSContext* cx, JS::Handle<JSObject*> global,
+    JS::Handle<JSObject*> protoProto, const JSClass* protoClass,
+    JS::Heap<JSObject*>* protoCache, JS::Handle<JSObject*> constructorProto,
+    const JSClass* constructorClass, unsigned ctorNargs,
+    bool isConstructorChromeOnly,
+    const LegacyFactoryFunction* namedConstructors,
+    JS::Heap<JSObject*>* constructorCache, const NativeProperties* properties,
+    const NativeProperties* chromeOnlyProperties, const char* name,
+    bool defineOnGlobal, const char* const* unscopableNames, bool isGlobal,
+    const char* const* legacyWindowAliases, bool isNamespace) {
+  MOZ_ASSERT(protoClass || constructorClass, "Need at least one class!");
+  MOZ_ASSERT(
+      !((properties &&
+         (properties->HasMethods() || properties->HasAttributes())) ||
+        (chromeOnlyProperties && (chromeOnlyProperties->HasMethods() ||
+                                  chromeOnlyProperties->HasAttributes()))) ||
+          protoClass,
+      "Methods or properties but no protoClass!");
+  MOZ_ASSERT(!((properties && (properties->HasStaticMethods() ||
+                               properties->HasStaticAttributes())) ||
+               (chromeOnlyProperties &&
+                (chromeOnlyProperties->HasStaticMethods() ||
+                 chromeOnlyProperties->HasStaticAttributes()))) ||
+                 constructorClass,
+             "Static methods but no constructorClass!");
+  MOZ_ASSERT(!protoClass == !protoCache,
+             "If, and only if, there is an interface prototype object we need "
+             "to cache it");
+  MOZ_ASSERT(bool(constructorClass) == bool(constructorCache),
+             "If, and only if, there is an interface object we need to cache "
+             "it");
+  MOZ_ASSERT(constructorProto || !constructorClass,
+             "Must have a constructor proto if we plan to create a constructor "
+             "object");
+
+  bool isChrome = nsContentUtils::ThreadsafeIsSystemCaller(cx);
+
+  JS::Rooted<JSString*> nameStr(cx, JS_AtomizeString(cx, name));
+  if (!nameStr) {
+    return;
+  }
+
+  JS::Rooted<JSObject*> proto(cx);
+  if (protoClass) {
+    proto = CreateInterfacePrototypeObject(
+        cx, global, protoProto, protoClass, properties,
+        isChrome ? chromeOnlyProperties : nullptr, unscopableNames, nameStr,
+        isGlobal);
+    if (!proto) {
+      return;
+    }
+
+    *protoCache = proto;
+  } else {
+    MOZ_ASSERT(!proto);
+  }
+
+  JSObject* interface;
+  if (constructorClass) {
+    interface = CreateInterfaceObject(
+        cx, global, constructorProto, constructorClass,
+        (isChrome || !isConstructorChromeOnly) ? ctorNargs : 0,
+        namedConstructors, proto, properties, chromeOnlyProperties, nameStr,
+        isChrome, defineOnGlobal, legacyWindowAliases, isNamespace);
+    if (!interface) {
+      if (protoCache) {
+        // If we fail we need to make sure to clear the value of protoCache we
+        // set above.
+        *protoCache = nullptr;
+      }
+      return;
+    }
+    *constructorCache = interface;
+  }
+}
+
+// Only set aAllowNativeWrapper to false if you really know you need it; if in
+// doubt use true. Setting it to false disables security wrappers.
+static bool NativeInterface2JSObjectAndThrowIfFailed(
+    JSContext* aCx, JS::Handle<JSObject*> aScope,
+    JS::MutableHandle<JS::Value> aRetval, xpcObjectHelper& aHelper,
+    const nsIID* aIID, bool aAllowNativeWrapper) {
+  js::AssertSameCompartment(aCx, aScope);
+  nsresult rv;
+  // Inline some logic from XPCConvert::NativeInterfaceToJSObject that we need
+  // on all threads.
+  nsWrapperCache* cache = aHelper.GetWrapperCache();
+
+  if (cache) {
+    JS::Rooted<JSObject*> obj(aCx, cache->GetWrapper());
+    if (!obj) {
+      obj = cache->WrapObject(aCx, nullptr);
+      if (!obj) {
+        return Throw(aCx, NS_ERROR_UNEXPECTED);
+      }
+    }
+
+    if (aAllowNativeWrapper && !JS_WrapObject(aCx, &obj)) {
+      return false;
+    }
+
+    aRetval.setObject(*obj);
+    return true;
+  }
+
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!XPCConvert::NativeInterface2JSObject(aCx, aRetval, aHelper, aIID,
+                                            aAllowNativeWrapper, &rv)) {
+    // I can't tell if NativeInterface2JSObject throws JS exceptions
+    // or not.  This is a sloppy stab at the right semantics; the
+    // method really ought to be fixed to behave consistently.
+    if (!JS_IsExceptionPending(aCx)) {
+      Throw(aCx, NS_FAILED(rv) ? rv : NS_ERROR_UNEXPECTED);
+    }
+    return false;
+  }
+  return true;
+}
+
+bool TryPreserveWrapper(JS::Handle<JSObject*> obj) {
+  MOZ_ASSERT(IsDOMObject(obj));
+
+  // nsISupports objects are special cased because DOM proxies are nsISupports
+  // and have addProperty hooks that do more than wrapper preservation (so we
+  // don't want to call them).
+  if (nsISupports* native = UnwrapDOMObjectToISupports(obj)) {
+    nsWrapperCache* cache = nullptr;
+    CallQueryInterface(native, &cache);
+    if (cache) {
+      cache->PreserveWrapper(native);
+    }
+    return true;
+  }
+
+  // The addProperty hook for WebIDL classes does wrapper preservation, and
+  // nothing else, so call it, if present.
+
+  const JSClass* clasp = JS::GetClass(obj);
+  const DOMJSClass* domClass = GetDOMClass(clasp);
+
+  // We expect all proxies to be nsISupports.
+  MOZ_RELEASE_ASSERT(clasp->isNativeObject(),
+                     "Should not call addProperty for proxies.");
+
+  JSAddPropertyOp addProperty = clasp->getAddProperty();
+  if (!addProperty) {
+    return true;
+  }
+
+  // The class should have an addProperty hook iff it is a CC participant.
+  MOZ_RELEASE_ASSERT(domClass->mParticipant);
+
+  JS::Rooted<jsid> dummyId(RootingCx());
+  JS::Rooted<JS::Value> dummyValue(RootingCx());
+  return addProperty(nullptr, obj, dummyId, dummyValue);
+}
+
+bool HasReleasedWrapper(JS::Handle<JSObject*> obj) {
+  MOZ_ASSERT(obj);
+  MOZ_ASSERT(IsDOMObject(obj));
+
+  nsWrapperCache* cache = nullptr;
+  if (nsISupports* native = UnwrapDOMObjectToISupports(obj)) {
+    CallQueryInterface(native, &cache);
+  } else {
+    const JSClass* clasp = JS::GetClass(obj);
+    const DOMJSClass* domClass = GetDOMClass(clasp);
+
+    // We expect all proxies to be nsISupports.
+    MOZ_RELEASE_ASSERT(clasp->isNativeObject(),
+                       "Should not call getWrapperCache for proxies.");
+
+    WrapperCacheGetter getter = domClass->mWrapperCacheGetter;
+
+    if (getter) {
+      // If the class has a wrapper cache getter it must be a CC participant.
+      MOZ_RELEASE_ASSERT(domClass->mParticipant);
+
+      cache = getter(obj);
+    }
+  }
+
+  return cache && !cache->PreservingWrapper();
+}
+
+// Can only be called with a DOM JSClass.
+bool InstanceClassHasProtoAtDepth(const JSClass* clasp, uint32_t protoID,
+                                  uint32_t depth) {
+  const DOMJSClass* domClass = DOMJSClass::FromJSClass(clasp);
+  return static_cast<uint32_t>(domClass->mInterfaceChain[depth]) == protoID;
+}
+
+// Only set allowNativeWrapper to false if you really know you need it; if in
+// doubt use true. Setting it to false disables security wrappers.
+bool XPCOMObjectToJsval(JSContext* cx, JS::Handle<JSObject*> scope,
+                        xpcObjectHelper& helper, const nsIID* iid,
+                        bool allowNativeWrapper,
+                        JS::MutableHandle<JS::Value> rval) {
+  return NativeInterface2JSObjectAndThrowIfFailed(cx, scope, rval, helper, iid,
+                                                  allowNativeWrapper);
+}
+
+bool VariantToJsval(JSContext* aCx, nsIVariant* aVariant,
+                    JS::MutableHandle<JS::Value> aRetval) {
+  nsresult rv;
+  if (!XPCVariant::VariantDataToJS(aCx, aVariant, &rv, aRetval)) {
+    // Does it throw?  Who knows
+    if (!JS_IsExceptionPending(aCx)) {
+      Throw(aCx, NS_FAILED(rv) ? rv : NS_ERROR_UNEXPECTED);
+    }
+    return false;
+  }
+
+  return true;
+}
+
+bool WrapObject(JSContext* cx, const WindowProxyHolder& p,
+                JS::MutableHandle<JS::Value> rval) {
+  return ToJSValue(cx, p, rval);
+}
+
+static int ComparePropertyInfosAtIndices(const void* aElement1,
+                                         const void* aElement2,
+                                         void* aClosure) {
+  const uint16_t index1 = *static_cast<const uint16_t*>(aElement1);
+  const uint16_t index2 = *static_cast<const uint16_t*>(aElement2);
+  const PropertyInfo* infos = static_cast<PropertyInfo*>(aClosure);
+
+  return PropertyInfo::Compare(infos[index1], infos[index2]);
+}
+
+// {JSPropertySpec,JSFunctionSpec} use {JSPropertySpec,JSFunctionSpec}::Name
+// and ConstantSpec uses `const char*` for name field.
+static inline JSPropertySpec::Name ToPropertySpecName(
+    JSPropertySpec::Name name) {
+  return name;
+}
+
+static inline JSPropertySpec::Name ToPropertySpecName(const char* name) {
+  return JSPropertySpec::Name(name);
+}
+
+template <typename SpecT>
+static bool InitPropertyInfos(JSContext* cx, const Prefable<SpecT>* pref,
+                              PropertyInfo* infos, PropertyType type) {
+  MOZ_ASSERT(pref);
+  MOZ_ASSERT(pref->specs);
+
+  // Index of the Prefable that contains the id for the current PropertyInfo.
+  uint32_t prefIndex = 0;
+
+  do {
+    // We ignore whether the set of ids is enabled and just intern all the IDs,
+    // because this is only done once per application runtime.
+    const SpecT* spec = pref->specs;
+    // Index of the property/function/constant spec for our current PropertyInfo
+    // in the "specs" array of the relevant Prefable.
+    uint32_t specIndex = 0;
+    do {
+      jsid id;
+      if (!JS::PropertySpecNameToPermanentId(cx, ToPropertySpecName(spec->name),
+                                             &id)) {
+        return false;
+      }
+      infos->SetId(id);
+      infos->type = type;
+      infos->prefIndex = prefIndex;
+      infos->specIndex = specIndex++;
+      ++infos;
+    } while ((++spec)->name);
+    ++prefIndex;
+  } while ((++pref)->specs);
+
+  return true;
+}
+
+#define INIT_PROPERTY_INFOS_IF_DEFINED(TypeName)                        \
+  {                                                                     \
+    if (nativeProperties->Has##TypeName##s() &&                         \
+        !InitPropertyInfos(cx, nativeProperties->TypeName##s(),         \
+                           nativeProperties->TypeName##PropertyInfos(), \
+                           e##TypeName)) {                              \
+      return false;                                                     \
+    }                                                                   \
+  }
+
+static bool InitPropertyInfos(JSContext* cx,
+                              const NativeProperties* nativeProperties) {
+  INIT_PROPERTY_INFOS_IF_DEFINED(StaticMethod);
+  INIT_PROPERTY_INFOS_IF_DEFINED(StaticAttribute);
+  INIT_PROPERTY_INFOS_IF_DEFINED(Method);
+  INIT_PROPERTY_INFOS_IF_DEFINED(Attribute);
+  INIT_PROPERTY_INFOS_IF_DEFINED(UnforgeableMethod);
+  INIT_PROPERTY_INFOS_IF_DEFINED(UnforgeableAttribute);
+  INIT_PROPERTY_INFOS_IF_DEFINED(Constant);
+
+  // Initialize and sort the index array.
+  uint16_t* indices = nativeProperties->sortedPropertyIndices;
+  for (unsigned int i = 0; i < nativeProperties->propertyInfoCount; ++i) {
+    indices[i] = i;
+  }
+  // ComparePropertyInfosAtIndices() doesn't actually modify the PropertyInfo
+  // array, so the const_cast here is OK in spite of the signature of
+  // NS_QuickSort().
+  NS_QuickSort(indices, nativeProperties->propertyInfoCount, sizeof(uint16_t),
+               ComparePropertyInfosAtIndices,
+               const_cast<PropertyInfo*>(nativeProperties->PropertyInfos()));
+
+  return true;
+}
+
+#undef INIT_PROPERTY_INFOS_IF_DEFINED
+
+static inline bool InitPropertyInfos(
+    JSContext* aCx, const NativePropertiesHolder& nativeProperties) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  if (!*nativeProperties.inited) {
+    if (nativeProperties.regular &&
+        !InitPropertyInfos(aCx, nativeProperties.regular)) {
+      return false;
+    }
+    if (nativeProperties.chromeOnly &&
+        !InitPropertyInfos(aCx, nativeProperties.chromeOnly)) {
+      return false;
+    }
+    *nativeProperties.inited = true;
+  }
+
+  return true;
+}
+
+void GetInterfaceImpl(JSContext* aCx, nsIInterfaceRequestor* aRequestor,
+                      nsWrapperCache* aCache, JS::Handle<JS::Value> aIID,
+                      JS::MutableHandle<JS::Value> aRetval,
+                      ErrorResult& aError) {
+  Maybe<nsIID> iid = xpc::JSValue2ID(aCx, aIID);
+  if (!iid) {
+    aError.Throw(NS_ERROR_XPC_BAD_CONVERT_JS);
+    return;
+  }
+
+  RefPtr<nsISupports> result;
+  aError = aRequestor->GetInterface(*iid, getter_AddRefs(result));
+  if (aError.Failed()) {
+    return;
+  }
+
+  if (!WrapObject(aCx, result, iid.ptr(), aRetval)) {
+    aError.Throw(NS_ERROR_FAILURE);
+  }
+}
+
+bool ThrowingConstructor(JSContext* cx, unsigned argc, JS::Value* vp) {
+  // Cast nullptr to void* to work around
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100666
+  return ThrowErrorMessage<MSG_ILLEGAL_CONSTRUCTOR>(cx, (void*)nullptr);
+}
+
+bool ThrowConstructorWithoutNew(JSContext* cx, const char* name) {
+  return ThrowErrorMessage<MSG_CONSTRUCTOR_WITHOUT_NEW>(cx, name);
+}
+
+inline const NativePropertyHooks* GetNativePropertyHooksFromConstructorFunction(
+    JS::Handle<JSObject*> obj) {
+  MOZ_ASSERT(JS_IsNativeFunction(obj, Constructor));
+  const JS::Value& v = js::GetFunctionNativeReserved(
+      obj, CONSTRUCTOR_NATIVE_HOLDER_RESERVED_SLOT);
+  const JSNativeHolder* nativeHolder =
+      static_cast<const JSNativeHolder*>(v.toPrivate());
+  return nativeHolder->mPropertyHooks;
+}
+
+inline const NativePropertyHooks* GetNativePropertyHooks(
+    JSContext* cx, JS::Handle<JSObject*> obj, DOMObjectType& type) {
+  const JSClass* clasp = JS::GetClass(obj);
+
+  const DOMJSClass* domClass = GetDOMClass(clasp);
+  if (domClass) {
+    bool isGlobal = (clasp->flags & JSCLASS_DOM_GLOBAL) != 0;
+    type = isGlobal ? eGlobalInstance : eInstance;
+    return domClass->mNativeHooks;
+  }
+
+  if (JS_ObjectIsFunction(obj)) {
+    type = eInterface;
+    return GetNativePropertyHooksFromConstructorFunction(obj);
+  }
+
+  MOZ_ASSERT(IsDOMIfaceAndProtoClass(JS::GetClass(obj)));
+  const DOMIfaceAndProtoJSClass* ifaceAndProtoJSClass =
+      DOMIfaceAndProtoJSClass::FromJSClass(JS::GetClass(obj));
+  type = ifaceAndProtoJSClass->mType;
+  return ifaceAndProtoJSClass->mNativeHooks;
+}
+
+static JSObject* XrayCreateFunction(JSContext* cx,
+                                    JS::Handle<JSObject*> wrapper,
+                                    JSNativeWrapper native, unsigned nargs,
+                                    JS::Handle<jsid> id) {
+  JSFunction* fun;
+  if (id.isString()) {
+    fun = js::NewFunctionByIdWithReserved(cx, native.op, nargs, 0, id);
+  } else {
+    // Can't pass this id (probably a symbol) to NewFunctionByIdWithReserved;
+    // just use an empty name for lack of anything better.
+    fun = js::NewFunctionWithReserved(cx, native.op, nargs, 0, nullptr);
+  }
+
+  if (!fun) {
+    return nullptr;
+  }
+
+  SET_JITINFO(fun, native.info);
+  JSObject* obj = JS_GetFunctionObject(fun);
+  js::SetFunctionNativeReserved(obj, XRAY_DOM_FUNCTION_PARENT_WRAPPER_SLOT,
+                                JS::ObjectValue(*wrapper));
+#ifdef DEBUG
+  js::SetFunctionNativeReserved(obj, XRAY_DOM_FUNCTION_NATIVE_SLOT_FOR_SELF,
+                                JS::ObjectValue(*obj));
+#endif
+  return obj;
+}
+
+struct IdToIndexComparator {
+  // The id we're searching for.
+  const jsid& mId;
+  // Whether we're searching for static operations.
+  const bool mStatic;
+  // The list of ids we're searching in.
+  const PropertyInfo* mInfos;
+
+  IdToIndexComparator(const jsid& aId, DOMObjectType aType,
+                      const PropertyInfo* aInfos)
+      : mId(aId),
+        mStatic(aType == eInterface || aType == eNamespace),
+        mInfos(aInfos) {}
+  int operator()(const uint16_t aIndex) const {
+    const PropertyInfo& info = mInfos[aIndex];
+    if (mId.asRawBits() == info.Id().asRawBits()) {
+      if (info.type != eMethod && info.type != eStaticMethod) {
+        return 0;
+      }
+
+      if (mStatic == info.IsStaticMethod()) {
+        // We're looking for static properties and we've found a static one for
+        // the right name.
+        return 0;
+      }
+
+      // Static operations are sorted before others by PropertyInfo::Compare.
+      return mStatic ? -1 : 1;
+    }
+
+    return mId.asRawBits() < info.Id().asRawBits() ? -1 : 1;
+  }
+};
+
+static const PropertyInfo* XrayFindOwnPropertyInfo(
+    JSContext* cx, DOMObjectType type, JS::Handle<jsid> id,
+    const NativeProperties* nativeProperties) {
+  if ((type == eInterfacePrototype || type == eGlobalInstance) &&
+      MOZ_UNLIKELY(nativeProperties->iteratorAliasMethodIndex >= 0) &&
+      id.isWellKnownSymbol(JS::SymbolCode::iterator)) {
+    return nativeProperties->MethodPropertyInfos() +
+           nativeProperties->iteratorAliasMethodIndex;
+  }
+
+  size_t idx;
+  const uint16_t* sortedPropertyIndices =
+      nativeProperties->sortedPropertyIndices;
+  const PropertyInfo* propertyInfos = nativeProperties->PropertyInfos();
+
+  if (BinarySearchIf(sortedPropertyIndices, 0,
+                     nativeProperties->propertyInfoCount,
+                     IdToIndexComparator(id, type, propertyInfos), &idx)) {
+    return propertyInfos + sortedPropertyIndices[idx];
+  }
+
+  return nullptr;
+}
+
+static bool XrayResolveAttribute(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid> id, const Prefable<const JSPropertySpec>& pref,
+    const JSPropertySpec& attrSpec,
+    JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder) {
+  if (!pref.isEnabled(cx, obj)) {
+    return true;
+  }
+
+  MOZ_ASSERT(attrSpec.isAccessor());
+
+  MOZ_ASSERT(
+      !attrSpec.isSelfHosted(),
+      "Bad JSPropertySpec declaration: unsupported self-hosted accessor");
+
+  cacheOnHolder = true;
+
+  JS::Rooted<jsid> getterId(cx);
+  if (!JS::ToGetterId(cx, id, &getterId)) {
+    return false;
+  }
+
+  // Because of centralization, we need to make sure we fault in the JitInfos as
+  // well. At present, until the JSAPI changes, the easiest way to do this is
+  // wrap them up as functions ourselves.
+
+  // They all have getters, so we can just make it.
+  JS::Rooted<JSObject*> getter(
+      cx, XrayCreateFunction(cx, wrapper, attrSpec.u.accessors.getter.native, 0,
+                             getterId));
+  if (!getter) {
+    return false;
+  }
+
+  JS::Rooted<JSObject*> setter(cx);
+  if (attrSpec.u.accessors.setter.native.op) {
+    JS::Rooted<jsid> setterId(cx);
+    if (!JS::ToSetterId(cx, id, &setterId)) {
+      return false;
+    }
+
+    // We have a setter! Make it.
+    setter = XrayCreateFunction(cx, wrapper, attrSpec.u.accessors.setter.native,
+                                1, setterId);
+    if (!setter) {
+      return false;
+    }
+  }
+
+  desc.set(Some(
+      JS::PropertyDescriptor::Accessor(getter, setter, attrSpec.attributes())));
+  return true;
+}
+
+static bool XrayResolveMethod(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid> id, const Prefable<const JSFunctionSpec>& pref,
+    const JSFunctionSpec& methodSpec,
+    JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder) {
+  if (!pref.isEnabled(cx, obj)) {
+    return true;
+  }
+
+  cacheOnHolder = true;
+
+  JSObject* funobj;
+  if (methodSpec.selfHostedName) {
+    JSFunction* fun = JS::GetSelfHostedFunction(cx, methodSpec.selfHostedName,
+                                                id, methodSpec.nargs);
+    if (!fun) {
+      return false;
+    }
+    MOZ_ASSERT(!methodSpec.call.op,
+               "Bad FunctionSpec declaration: non-null native");
+    MOZ_ASSERT(!methodSpec.call.info,
+               "Bad FunctionSpec declaration: non-null jitinfo");
+    funobj = JS_GetFunctionObject(fun);
+  } else {
+    funobj =
+        XrayCreateFunction(cx, wrapper, methodSpec.call, methodSpec.nargs, id);
+    if (!funobj) {
+      return false;
+    }
+  }
+
+  desc.set(Some(JS::PropertyDescriptor::Data(JS::ObjectValue(*funobj),
+                                             methodSpec.flags)));
+  return true;
+}
+
+static bool XrayResolveConstant(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid>, const Prefable<const ConstantSpec>& pref,
+    const ConstantSpec& constantSpec,
+    JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder) {
+  if (!pref.isEnabled(cx, obj)) {
+    return true;
+  }
+
+  cacheOnHolder = true;
+
+  desc.set(Some(JS::PropertyDescriptor::Data(
+      constantSpec.value, {JS::PropertyAttribute::Enumerable})));
+  return true;
+}
+
+#define RESOLVE_CASE(PropType, SpecType, Resolver)                            \
+  case e##PropType: {                                                         \
+    MOZ_ASSERT(nativeProperties->Has##PropType##s());                         \
+    const Prefable<const SpecType>& pref =                                    \
+        nativeProperties->PropType##s()[propertyInfo.prefIndex];              \
+    return Resolver(cx, wrapper, obj, id, pref,                               \
+                    pref.specs[propertyInfo.specIndex], desc, cacheOnHolder); \
+  }
+
+static bool XrayResolveProperty(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid> id, JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder, DOMObjectType type,
+    const NativeProperties* nativeProperties,
+    const PropertyInfo& propertyInfo) {
+  MOZ_ASSERT(type != eGlobalInterfacePrototype);
+
+  // Make sure we resolve for matched object type.
+  switch (propertyInfo.type) {
+    case eStaticMethod:
+    case eStaticAttribute:
+      if (type != eInterface && type != eNamespace) {
+        return true;
+      }
+      break;
+    case eMethod:
+    case eAttribute:
+      if (type != eGlobalInstance && type != eInterfacePrototype) {
+        return true;
+      }
+      break;
+    case eUnforgeableMethod:
+    case eUnforgeableAttribute:
+      if (!IsInstance(type)) {
+        return true;
+      }
+      break;
+    case eConstant:
+      if (IsInstance(type)) {
+        return true;
+      }
+      break;
+  }
+
+  switch (propertyInfo.type) {
+    RESOLVE_CASE(StaticMethod, JSFunctionSpec, XrayResolveMethod)
+    RESOLVE_CASE(StaticAttribute, JSPropertySpec, XrayResolveAttribute)
+    RESOLVE_CASE(Method, JSFunctionSpec, XrayResolveMethod)
+    RESOLVE_CASE(Attribute, JSPropertySpec, XrayResolveAttribute)
+    RESOLVE_CASE(UnforgeableMethod, JSFunctionSpec, XrayResolveMethod)
+    RESOLVE_CASE(UnforgeableAttribute, JSPropertySpec, XrayResolveAttribute)
+    RESOLVE_CASE(Constant, ConstantSpec, XrayResolveConstant)
+  }
+
+  return true;
+}
+
+#undef RESOLVE_CASE
+
+static bool ResolvePrototypeOrConstructor(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    size_t protoAndIfaceCacheIndex, unsigned attrs,
+    JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder) {
+  JS::Rooted<JSObject*> global(cx, JS::GetNonCCWObjectGlobal(obj));
+  {
+    JSAutoRealm ar(cx, global);
+    ProtoAndIfaceCache& protoAndIfaceCache = *GetProtoAndIfaceCache(global);
+    // This function is called when resolving the "constructor" and "prototype"
+    // properties of Xrays for DOM prototypes and constructors respectively.
+    // This means the relevant Xray exists, which means its _target_ exists.
+    // And that means we managed to successfullly create the prototype or
+    // constructor, respectively, and hence must have managed to create the
+    // thing it's pointing to as well.  So our entry slot must exist.
+    JSObject* protoOrIface =
+        protoAndIfaceCache.EntrySlotMustExist(protoAndIfaceCacheIndex);
+    MOZ_RELEASE_ASSERT(protoOrIface, "How can this object not exist?");
+
+    cacheOnHolder = true;
+
+    desc.set(Some(
+        JS::PropertyDescriptor::Data(JS::ObjectValue(*protoOrIface), attrs)));
+  }
+  return JS_WrapPropertyDescriptor(cx, desc);
+}
+
+/* static */ bool XrayResolveOwnProperty(
+    JSContext* cx, JS::Handle<JSObject*> wrapper, JS::Handle<JSObject*> obj,
+    JS::Handle<jsid> id, JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc,
+    bool& cacheOnHolder) {
+  MOZ_ASSERT(desc.isNothing());
+  cacheOnHolder = false;
+
+  DOMObjectType type;
+  const NativePropertyHooks* nativePropertyHooks =
+      GetNativePropertyHooks(cx, obj, type);
+  ResolveOwnProperty resolveOwnProperty =
+      nativePropertyHooks->mResolveOwnProperty;
+
+  if (type == eNamedPropertiesObject) {
+    MOZ_ASSERT(!resolveOwnProperty,
+               "Shouldn't have any Xray-visible properties");
+    return true;
+  }
+
+  const NativePropertiesHolder& nativePropertiesHolder =
+      nativePropertyHooks->mNativeProperties;
+
+  if (!InitPropertyInfos(cx, nativePropertiesHolder)) {
+    return false;
+  }
+
+  const NativeProperties* nativeProperties = nullptr;
+  const PropertyInfo* found = nullptr;
+
+  if ((nativeProperties = nativePropertiesHolder.regular)) {
+    found = XrayFindOwnPropertyInfo(cx, type, id, nativeProperties);
+  }
+  if (!found && (nativeProperties = nativePropertiesHolder.chromeOnly) &&
+      xpc::AccessCheck::isChrome(JS::GetCompartment(wrapper))) {
+    found = XrayFindOwnPropertyInfo(cx, type, id, nativeProperties);
+  }
+
+  if (IsInstance(type)) {
+    // Check for unforgeable properties first to prevent names provided by
+    // resolveOwnProperty callback from shadowing them.
+    if (found && (found->type == eUnforgeableMethod ||
+                  found->type == eUnforgeableAttribute)) {
+      if (!XrayResolveProperty(cx, wrapper, obj, id, desc, cacheOnHolder, type,
+                               nativeProperties, *found)) {
+        return false;
+      }
+
+      if (desc.isSome()) {
+        return true;
+      }
+    }
+
+    if (resolveOwnProperty) {
+      if (!resolveOwnProperty(cx, wrapper, obj, id, desc)) {
+        return false;
+      }
+
+      if (desc.isSome()) {
+        // None of these should be cached on the holder, since they're dynamic.
+        return true;
+      }
+    }
+
+    // For non-global instance Xrays there are no other properties, so return
+    // here for them.
+    if (type != eGlobalInstance) {
+      return true;
+    }
+  } else if (type == eInterface) {
+    if (id.get() == GetJSIDByIndex(cx, XPCJSContext::IDX_PROTOTYPE)) {
+      return nativePropertyHooks->mPrototypeID == prototypes::id::_ID_Count ||
+             ResolvePrototypeOrConstructor(
+                 cx, wrapper, obj, nativePropertyHooks->mPrototypeID,
+                 JSPROP_PERMANENT | JSPROP_READONLY, desc, cacheOnHolder);
+    }
+
+    if (id.get() == GetJSIDByIndex(cx, XPCJSContext::IDX_ISINSTANCE)) {
+      const JSClass* objClass = JS::GetClass(obj);
+      if (IsDOMIfaceAndProtoClass(objClass) &&
+          DOMIfaceAndProtoJSClass::FromJSClass(objClass)
+              ->wantsInterfaceHasInstance) {
+        cacheOnHolder = true;
+        JSNativeWrapper interfaceIsInstanceWrapper = {InterfaceIsInstance,
+                                                      nullptr};
+        JSObject* funObj =
+            XrayCreateFunction(cx, wrapper, interfaceIsInstanceWrapper, 1, id);
+        if (!funObj) {
+          return false;
+        }
+
+        desc.set(Some(JS::PropertyDescriptor::Data(
+            JS::ObjectValue(*funObj), {JS::PropertyAttribute::Configurable,
+                                       JS::PropertyAttribute::Writable})));
+        return true;
+      }
+    }
+
+    if (StaticPrefs::dom_webidl_crosscontext_hasinstance_enabled() &&
+        id.isWellKnownSymbol(JS::SymbolCode::hasInstance)) {
+      const JSClass* objClass = JS::GetClass(obj);
+      if (IsDOMIfaceAndProtoClass(objClass) &&
+          DOMIfaceAndProtoJSClass::FromJSClass(objClass)
+              ->wantsInterfaceHasInstance) {
+        cacheOnHolder = true;
+        JSNativeWrapper interfaceHasInstanceWrapper = {InterfaceHasInstance,
+                                                       nullptr};
+        JSObject* funObj =
+            XrayCreateFunction(cx, wrapper, interfaceHasInstanceWrapper, 1, id);
+        if (!funObj) {
+          return false;
+        }
+
+        desc.set(
+            Some(JS::PropertyDescriptor::Data(JS::ObjectValue(*funObj), {})));
+        return true;
+      }
+    }
+  } else if (type == eNamespace) {
+    if (id.isWellKnownSymbol(JS::SymbolCode::toStringTag)) {
+      JS::Rooted<JSString*> nameStr(
+          cx, JS_AtomizeString(cx, JS::GetClass(obj)->name));
+      if (!nameStr) {
+        return false;
+      }
+
+      desc.set(Some(JS::PropertyDescriptor::Data(
+          JS::StringValue(nameStr), {JS::PropertyAttribute::Configurable})));
+      return true;
+    }
+  } else {
+    MOZ_ASSERT(IsInterfacePrototype(type));
+
+    if (id.get() == GetJSIDByIndex(cx, XPCJSContext::IDX_CONSTRUCTOR)) {
+      return nativePropertyHooks->mConstructorID ==
+                 constructors::id::_ID_Count ||
+             ResolvePrototypeOrConstructor(cx, wrapper, obj,
+                                           nativePropertyHooks->mConstructorID,
+                                           0, desc, cacheOnHolder);
+    }
+
+    if (id.isWellKnownSymbol(JS::SymbolCode::toStringTag)) {
+      const JSClass* objClass = JS::GetClass(obj);
+      prototypes::ID prototypeID =
+          DOMIfaceAndProtoJSClass::FromJSClass(objClass)->mPrototypeID;
+      JS::Rooted<JSString*> nameStr(
+          cx, JS_AtomizeString(cx, NamesOfInterfacesWithProtos(prototypeID)));
+      if (!nameStr) {
+        return false;
+      }
+
+      desc.set(Some(JS::PropertyDescriptor::Data(
+          JS::StringValue(nameStr), {JS::PropertyAttribute::Configurable})));
+      return true;
+    }
+
+    // The properties for globals live on the instance, so return here as there
+    // are no properties on their interface prototype object.
+    if (type == eGlobalInterfacePrototype) {
+      return true;
+    }
+  }
+
+  if (found && !XrayResolveProperty(cx, wrapper, obj, id, desc, cacheOnHolder,
+                                    type, nativeProperties, *found)) {
+    return false;
+  }
+
+  return true;
+}
+
+bool XrayDefineProperty(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                        JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+                        JS::Handle<JS::PropertyDescriptor> desc,
+                        JS::ObjectOpResult& result, bool* done) {
+  if (!js::IsProxy(obj)) return true;
+
+  const DOMProxyHandler* handler = GetDOMProxyHandler(obj);
+  return handler->defineProperty(cx, wrapper, id, desc, result, done);
+}
+
+template <typename SpecType>
+bool XrayAppendPropertyKeys(JSContext* cx, JS::Handle<JSObject*> obj,
+                            const Prefable<const SpecType>* pref,
+                            const PropertyInfo* infos, unsigned flags,
+                            JS::MutableHandleVector<jsid> props) {
+  do {
+    bool prefIsEnabled = pref->isEnabled(cx, obj);
+    if (prefIsEnabled) {
+      const SpecType* spec = pref->specs;
+      do {
+        const jsid id = infos++->Id();
+        if (((flags & JSITER_HIDDEN) ||
+             (spec->attributes() & JSPROP_ENUMERATE)) &&
+            ((flags & JSITER_SYMBOLS) || !id.isSymbol()) && !props.append(id)) {
+          return false;
+        }
+      } while ((++spec)->name);
+    }
+    // Break if we have reached the end of pref.
+    if (!(++pref)->specs) {
+      break;
+    }
+    // Advance infos if the previous pref is disabled. The -1 is required
+    // because there is an end-of-list terminator between pref->specs and
+    // (pref - 1)->specs.
+    if (!prefIsEnabled) {
+      infos += pref->specs - (pref - 1)->specs - 1;
+    }
+  } while (1);
+
+  return true;
+}
+
+template <>
+bool XrayAppendPropertyKeys<ConstantSpec>(
+    JSContext* cx, JS::Handle<JSObject*> obj,
+    const Prefable<const ConstantSpec>* pref, const PropertyInfo* infos,
+    unsigned flags, JS::MutableHandleVector<jsid> props) {
+  do {
+    bool prefIsEnabled = pref->isEnabled(cx, obj);
+    if (prefIsEnabled) {
+      const ConstantSpec* spec = pref->specs;
+      do {
+        if (!props.append(infos++->Id())) {
+          return false;
+        }
+      } while ((++spec)->name);
+    }
+    // Break if we have reached the end of pref.
+    if (!(++pref)->specs) {
+      break;
+    }
+    // Advance infos if the previous pref is disabled. The -1 is required
+    // because there is an end-of-list terminator between pref->specs and
+    // (pref - 1)->specs.
+    if (!prefIsEnabled) {
+      infos += pref->specs - (pref - 1)->specs - 1;
+    }
+  } while (1);
+
+  return true;
+}
+
+#define ADD_KEYS_IF_DEFINED(FieldName)                                        \
+  {                                                                           \
+    if (nativeProperties->Has##FieldName##s() &&                              \
+        !XrayAppendPropertyKeys(cx, obj, nativeProperties->FieldName##s(),    \
+                                nativeProperties->FieldName##PropertyInfos(), \
+                                flags, props)) {                              \
+      return false;                                                           \
+    }                                                                         \
+  }
+
+bool XrayOwnPropertyKeys(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                         JS::Handle<JSObject*> obj, unsigned flags,
+                         JS::MutableHandleVector<jsid> props,
+                         DOMObjectType type,
+                         const NativeProperties* nativeProperties) {
+  MOZ_ASSERT(type != eNamedPropertiesObject);
+
+  if (IsInstance(type)) {
+    ADD_KEYS_IF_DEFINED(UnforgeableMethod);
+    ADD_KEYS_IF_DEFINED(UnforgeableAttribute);
+    if (type == eGlobalInstance) {
+      ADD_KEYS_IF_DEFINED(Method);
+      ADD_KEYS_IF_DEFINED(Attribute);
+    }
+  } else {
+    MOZ_ASSERT(type != eGlobalInterfacePrototype);
+    if (type == eInterface || type == eNamespace) {
+      ADD_KEYS_IF_DEFINED(StaticMethod);
+      ADD_KEYS_IF_DEFINED(StaticAttribute);
+    } else {
+      MOZ_ASSERT(type == eInterfacePrototype);
+      ADD_KEYS_IF_DEFINED(Method);
+      ADD_KEYS_IF_DEFINED(Attribute);
+    }
+    ADD_KEYS_IF_DEFINED(Constant);
+  }
+
+  return true;
+}
+
+#undef ADD_KEYS_IF_DEFINED
+
+bool XrayOwnNativePropertyKeys(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                               const NativePropertyHooks* nativePropertyHooks,
+                               DOMObjectType type, JS::Handle<JSObject*> obj,
+                               unsigned flags,
+                               JS::MutableHandleVector<jsid> props) {
+  MOZ_ASSERT(type != eNamedPropertiesObject);
+
+  if (type == eInterface &&
+      nativePropertyHooks->mPrototypeID != prototypes::id::_ID_Count &&
+      !AddStringToIDVector(cx, props, "prototype")) {
+    return false;
+  }
+
+  if (IsInterfacePrototype(type) &&
+      nativePropertyHooks->mConstructorID != constructors::id::_ID_Count &&
+      (flags & JSITER_HIDDEN) &&
+      !AddStringToIDVector(cx, props, "constructor")) {
+    return false;
+  }
+
+  const NativePropertiesHolder& nativeProperties =
+      nativePropertyHooks->mNativeProperties;
+
+  if (!InitPropertyInfos(cx, nativeProperties)) {
+    return false;
+  }
+
+  if (nativeProperties.regular &&
+      !XrayOwnPropertyKeys(cx, wrapper, obj, flags, props, type,
+                           nativeProperties.regular)) {
+    return false;
+  }
+
+  if (nativeProperties.chromeOnly &&
+      xpc::AccessCheck::isChrome(JS::GetCompartment(wrapper)) &&
+      !XrayOwnPropertyKeys(cx, wrapper, obj, flags, props, type,
+                           nativeProperties.chromeOnly)) {
+    return false;
+  }
+
+  return true;
+}
+
+bool XrayOwnPropertyKeys(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                         JS::Handle<JSObject*> obj, unsigned flags,
+                         JS::MutableHandleVector<jsid> props) {
+  DOMObjectType type;
+  const NativePropertyHooks* nativePropertyHooks =
+      GetNativePropertyHooks(cx, obj, type);
+  EnumerateOwnProperties enumerateOwnProperties =
+      nativePropertyHooks->mEnumerateOwnProperties;
+
+  if (type == eNamedPropertiesObject) {
+    MOZ_ASSERT(!enumerateOwnProperties,
+               "Shouldn't have any Xray-visible properties");
+    return true;
+  }
+
+  if (IsInstance(type)) {
+    // FIXME https://bugzilla.mozilla.org/show_bug.cgi?id=1071189
+    //       Should do something about XBL properties too.
+    if (enumerateOwnProperties &&
+        !enumerateOwnProperties(cx, wrapper, obj, props)) {
+      return false;
+    }
+  }
+
+  return type == eGlobalInterfacePrototype ||
+         XrayOwnNativePropertyKeys(cx, wrapper, nativePropertyHooks, type, obj,
+                                   flags, props);
+}
+
+const JSClass* XrayGetExpandoClass(JSContext* cx, JS::Handle<JSObject*> obj) {
+  DOMObjectType type;
+  const NativePropertyHooks* nativePropertyHooks =
+      GetNativePropertyHooks(cx, obj, type);
+  if (!IsInstance(type)) {
+    // Non-instances don't need any special expando classes.
+    return &DefaultXrayExpandoObjectClass;
+  }
+
+  return nativePropertyHooks->mXrayExpandoClass;
+}
+
+bool XrayDeleteNamedProperty(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                             JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+                             JS::ObjectOpResult& opresult) {
+  DOMObjectType type;
+  const NativePropertyHooks* nativePropertyHooks =
+      GetNativePropertyHooks(cx, obj, type);
+  if (!IsInstance(type) || !nativePropertyHooks->mDeleteNamedProperty) {
+    return opresult.succeed();
+  }
+  return nativePropertyHooks->mDeleteNamedProperty(cx, wrapper, obj, id,
+                                                   opresult);
+}
+
+namespace binding_detail {
+
+bool ResolveOwnProperty(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                        JS::Handle<JSObject*> obj, JS::Handle<jsid> id,
+                        JS::MutableHandle<Maybe<JS::PropertyDescriptor>> desc) {
+  return js::GetProxyHandler(obj)->getOwnPropertyDescriptor(cx, wrapper, id,
+                                                            desc);
+}
+
+bool EnumerateOwnProperties(JSContext* cx, JS::Handle<JSObject*> wrapper,
+                            JS::Handle<JSObject*> obj,
+                            JS::MutableHandleVector<jsid> props) {
+  return js::GetProxyHandler(obj)->ownPropertyKeys(cx, wrapper, props);
+}
+
+}  // namespace binding_detail
+
+JSObject* GetCachedSlotStorageObjectSlow(JSContext* cx,
+                                         JS::Handle<JSObject*> obj,
+                                         bool* isXray) {
+  if (!xpc::WrapperFactory::IsXrayWrapper(obj)) {
+    JSObject* retval =
+        js::UncheckedUnwrap(obj, /* stopAtWindowProxy = */ false);
+    MOZ_ASSERT(IsDOMObject(retval));
+    *isXray = false;
+    return retval;
+  }
+
+  *isXray = true;
+  return xpc::EnsureXrayExpandoObject(cx, obj);
+}
+
+DEFINE_XRAY_EXPANDO_CLASS(, DefaultXrayExpandoObjectClass, 0);
+
+bool sEmptyNativePropertiesInited = true;
+NativePropertyHooks sEmptyNativePropertyHooks = {
+    nullptr,
+    nullptr,
+    nullptr,
+    {nullptr, nullptr, &sEmptyNativePropertiesInited},
+    prototypes::id::_ID_Count,
+    constructors::id::_ID_Count,
+    nullptr};
+
+const JSClassOps sBoringInterfaceObjectClassClassOps = {
+    nullptr,             /* addProperty */
+    nullptr,             /* delProperty */
+    nullptr,             /* enumerate */
+    nullptr,             /* newEnumerate */
+    nullptr,             /* resolve */
+    nullptr,             /* mayResolve */
+    nullptr,             /* finalize */
+    ThrowingConstructor, /* call */
+    ThrowingConstructor, /* construct */
+    nullptr,             /* trace */
+};
+
+const js::ObjectOps sInterfaceObjectClassObjectOps = {
+    nullptr,                 /* lookupProperty */
+    nullptr,                 /* defineProperty */
+    nullptr,                 /* hasProperty */
+    nullptr,                 /* getProperty */
+    nullptr,                 /* setProperty */
+    nullptr,                 /* getOwnPropertyDescriptor */
+    nullptr,                 /* deleteProperty */
+    nullptr,                 /* getElements */
+    InterfaceObjectToString, /* funToString */
+};
+
+bool GetPropertyOnPrototype(JSContext* cx, JS::Handle<JSObject*> proxy,
+                            JS::Handle<JS::Value> receiver, JS::Handle<jsid> id,
+                            bool* found, JS::MutableHandle<JS::Value> vp) {
+  JS::Rooted<JSObject*> proto(cx);
+  if (!js::GetObjectProto(cx, proxy, &proto)) {
+    return false;
+  }
+  if (!proto) {
+    *found = false;
+    return true;
+  }
+
+  if (!JS_HasPropertyById(cx, proto, id, found)) {
+    return false;
+  }
+
+  if (!*found) {
+    return true;
+  }
+
+  return JS_ForwardGetPropertyTo(cx, proto, id, receiver, vp);
+}
+
+bool HasPropertyOnPrototype(JSContext* cx, JS::Handle<JSObject*> proxy,
+                            JS::Handle<jsid> id, bool* has) {
+  JS::Rooted<JSObject*> proto(cx);
+  if (!js::GetObjectProto(cx, proxy, &proto)) {
+    return false;
+  }
+  if (!proto) {
+    *has = false;
+    return true;
+  }
+
+  return JS_HasPropertyById(cx, proto, id, has);
+}
+
+bool AppendNamedPropertyIds(JSContext* cx, JS::Handle<JSObject*> proxy,
+                            nsTArray<nsString>& names,
+                            bool shadowPrototypeProperties,
+                            JS::MutableHandleVector<jsid> props) {
+  for (uint32_t i = 0; i < names.Length(); ++i) {
+    JS::Rooted<JS::Value> v(cx);
+    if (!xpc::NonVoidStringToJsval(cx, names[i], &v)) {
+      return false;
+    }
+
+    JS::Rooted<jsid> id(cx);
+    if (!JS_ValueToId(cx, v, &id)) {
+      return false;
+    }
+
+    bool shouldAppend = shadowPrototypeProperties;
+    if (!shouldAppend) {
+      bool has;
+      if (!HasPropertyOnPrototype(cx, proxy, id, &has)) {
+        return false;
+      }
+      shouldAppend = !has;
+    }
+
+    if (shouldAppend) {
+      if (!props.append(id)) {
+        return false;
+      }
+    }
+  }
+
+  return true;
+}
+
+bool DictionaryBase::ParseJSON(JSContext* aCx, const nsAString& aJSON,
+                               JS::MutableHandle<JS::Value> aVal) {
+  if (aJSON.IsEmpty()) {
+    return true;
+  }
+  return JS_ParseJSON(aCx, aJSON.BeginReading(), aJSON.Length(), aVal);
+}
+
+bool DictionaryBase::StringifyToJSON(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                                     nsAString& aJSON) const {
+  return JS::ToJSONMaybeSafely(aCx, aObj, AppendJSONToString, &aJSON);
+}
+
+/* static */
+bool DictionaryBase::AppendJSONToString(const char16_t* aJSONData,
+                                        uint32_t aDataLength, void* aString) {
+  nsAString* string = static_cast<nsAString*>(aString);
+  string->Append(aJSONData, aDataLength);
+  return true;
+}
+
+void UpdateReflectorGlobal(JSContext* aCx, JS::Handle<JSObject*> aObjArg,
+                           ErrorResult& aError) {
+  js::AssertSameCompartment(aCx, aObjArg);
+
+  aError.MightThrowJSException();
+
+  // Check if we're anywhere near the stack limit before we reach the
+  // transplanting code, since it has no good way to handle errors. This uses
+  // the untrusted script limit, which is not strictly necessary since no
+  // actual script should run.
+  js::AutoCheckRecursionLimit recursion(aCx);
+  if (!recursion.checkConservative(aCx)) {
+    aError.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  JS::Rooted<JSObject*> aObj(aCx, aObjArg);
+  MOZ_ASSERT(IsDOMObject(aObj));
+
+  const DOMJSClass* domClass = GetDOMClass(aObj);
+
+  JS::Rooted<JSObject*> oldGlobal(aCx, JS::GetNonCCWObjectGlobal(aObj));
+  MOZ_ASSERT(JS_IsGlobalObject(oldGlobal));
+
+  JS::Rooted<JSObject*> newGlobal(aCx,
+                                  domClass->mGetAssociatedGlobal(aCx, aObj));
+  MOZ_ASSERT(JS_IsGlobalObject(newGlobal));
+
+  JSAutoRealm oldAr(aCx, oldGlobal);
+
+  if (oldGlobal == newGlobal) {
+    return;
+  }
+
+  nsISupports* native = UnwrapDOMObjectToISupports(aObj);
+  if (!native) {
+    return;
+  }
+
+  bool isProxy = js::IsProxy(aObj);
+  JS::Rooted<JSObject*> expandoObject(aCx);
+  if (isProxy) {
+    expandoObject = DOMProxyHandler::GetAndClearExpandoObject(aObj);
+  }
+
+  JSAutoRealm newAr(aCx, newGlobal);
+
+  // First we clone the reflector. We get a copy of its properties and clone its
+  // expando chain.
+
+  JS::Handle<JSObject*> proto = (domClass->mGetProto)(aCx);
+  if (!proto) {
+    aError.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  JS::Rooted<JSObject*> newobj(aCx, JS_CloneObject(aCx, aObj, proto));
+  if (!newobj) {
+    aError.StealExceptionFromJSContext(aCx);
+    return;
+  }
+
+  // Assert it's possible to create wrappers when |aObj| and |newobj| are in
+  // different compartments.
+  MOZ_ASSERT_IF(JS::GetCompartment(aObj) != JS::GetCompartment(newobj),
+                js::AllowNewWrapper(JS::GetCompartment(aObj), newobj));
+
+  JS::Rooted<JSObject*> propertyHolder(aCx);
+  JS::Rooted<JSObject*> copyFrom(aCx, isProxy ? expandoObject : aObj);
+  if (copyFrom) {
+    propertyHolder = JS_NewObjectWithGivenProto(aCx, nullptr, nullptr);
+    if (!propertyHolder) {
+      aError.StealExceptionFromJSContext(aCx);
+      return;
+    }
+
+    if (!JS_CopyOwnPropertiesAndPrivateFields(aCx, propertyHolder, copyFrom)) {
+      aError.StealExceptionFromJSContext(aCx);
+      return;
+    }
+  } else {
+    propertyHolder = nullptr;
+  }
+
+  // We've set up |newobj|, so we make it own the native by setting its reserved
+  // slot and nulling out the reserved slot of |obj|. Update the wrapper cache
+  // to keep everything consistent in case GC moves newobj.
+  //
+  // NB: It's important to do this _after_ copying the properties to
+  // propertyHolder. Otherwise, an object with |foo.x === foo| will
+  // crash when JS_CopyOwnPropertiesAndPrivateFields tries to call wrap() on
+  // foo.x.
+  JS::SetReservedSlot(newobj, DOM_OBJECT_SLOT,
+                      JS::GetReservedSlot(aObj, DOM_OBJECT_SLOT));
+  JS::SetReservedSlot(aObj, DOM_OBJECT_SLOT, JS::PrivateValue(nullptr));
+  nsWrapperCache* cache = nullptr;
+  CallQueryInterface(native, &cache);
+  cache->UpdateWrapperForNewGlobal(native, newobj);
+
+  aObj = xpc::TransplantObjectRetainingXrayExpandos(aCx, aObj, newobj);
+  if (!aObj) {
+    MOZ_CRASH();
+  }
+
+  // Update the wrapper cache again if transplanting didn't use newobj but
+  // returned some other object.
+  if (aObj != newobj) {
+    MOZ_ASSERT(UnwrapDOMObjectToISupports(aObj) == native);
+    cache->UpdateWrapperForNewGlobal(native, aObj);
+  }
+
+  if (propertyHolder) {
+    JS::Rooted<JSObject*> copyTo(aCx);
+    if (isProxy) {
+      copyTo = DOMProxyHandler::EnsureExpandoObject(aCx, aObj);
+    } else {
+      copyTo = aObj;
+    }
+
+    if (!copyTo ||
+        !JS_CopyOwnPropertiesAndPrivateFields(aCx, copyTo, propertyHolder)) {
+      MOZ_CRASH();
+    }
+  }
+}
+
+GlobalObject::GlobalObject(JSContext* aCx, JSObject* aObject)
+    : mGlobalJSObject(aCx), mCx(aCx), mGlobalObject(nullptr) {
+  MOZ_ASSERT(mCx);
+  JS::Rooted<JSObject*> obj(aCx, aObject);
+  if (js::IsWrapper(obj)) {
+    // aCx correctly represents the current global here.
+    obj = js::CheckedUnwrapDynamic(obj, aCx, /* stopAtWindowProxy = */ false);
+    if (!obj) {
+      // We should never end up here on a worker thread, since there shouldn't
+      // be any security wrappers to worry about.
+      if (!MOZ_LIKELY(NS_IsMainThread())) {
+        MOZ_CRASH();
+      }
+
+      Throw(aCx, NS_ERROR_XPC_SECURITY_MANAGER_VETO);
+      return;
+    }
+  }
+
+  mGlobalJSObject = JS::GetNonCCWObjectGlobal(obj);
+}
+
+nsISupports* GlobalObject::GetAsSupports() const {
+  if (mGlobalObject) {
+    return mGlobalObject;
+  }
+
+  MOZ_ASSERT(!js::IsWrapper(mGlobalJSObject));
+
+  // Most of our globals are DOM objects.  Try that first.  Note that this
+  // assumes that either the first nsISupports in the object is the canonical
+  // one or that we don't care about the canonical nsISupports here.
+  mGlobalObject = UnwrapDOMObjectToISupports(mGlobalJSObject);
+  if (mGlobalObject) {
+    return mGlobalObject;
+  }
+
+  MOZ_ASSERT(NS_IsMainThread(), "All our worker globals are DOM objects");
+
+  // Remove everything below here once all our global objects are using new
+  // bindings.  If that ever happens; it would need to include Sandbox and
+  // BackstagePass.
+
+  // See whether mGlobalJSObject is an XPCWrappedNative.  This will redo the
+  // IsWrapper bit above and the UnwrapDOMObjectToISupports in the case when
+  // we're not actually an XPCWrappedNative, but this should be a rare-ish case
+  // anyway.
+  //
+  // It's OK to use ReflectorToISupportsStatic, because we know we don't have a
+  // cross-compartment wrapper.
+  nsCOMPtr<nsISupports> supp = xpc::ReflectorToISupportsStatic(mGlobalJSObject);
+  if (supp) {
+    // See documentation for mGlobalJSObject for why this assignment is OK.
+    mGlobalObject = supp;
+    return mGlobalObject;
+  }
+
+  // And now a final hack.  Sandbox is not a reflector, but it does have an
+  // nsIGlobalObject hanging out in its private slot.  Handle that case here,
+  // (though again, this will do the useless UnwrapDOMObjectToISupports if we
+  // got here for something that is somehow not a DOM object, not an
+  // XPCWrappedNative _and_ not a Sandbox).
+  if (XPCConvert::GetISupportsFromJSObject(mGlobalJSObject, &mGlobalObject)) {
+    return mGlobalObject;
+  }
+
+  MOZ_ASSERT(!mGlobalObject);
+
+  Throw(mCx, NS_ERROR_XPC_BAD_CONVERT_JS);
+  return nullptr;
+}
+
+nsIPrincipal* GlobalObject::GetSubjectPrincipal() const {
+  if (!NS_IsMainThread()) {
+    return nullptr;
+  }
+
+  JS::Realm* realm = js::GetContextRealm(mCx);
+  MOZ_ASSERT(realm);
+  JSPrincipals* principals = JS::GetRealmPrincipals(realm);
+  return nsJSPrincipals::get(principals);
+}
+
+CallerType GlobalObject::CallerType() const {
+  return nsContentUtils::ThreadsafeIsSystemCaller(mCx)
+             ? dom::CallerType::System
+             : dom::CallerType::NonSystem;
+}
+
+static bool CallOrdinaryHasInstance(JSContext* cx, JS::CallArgs& args) {
+  JS::Rooted<JSObject*> thisObj(cx, &args.thisv().toObject());
+  bool isInstance;
+  if (!JS::OrdinaryHasInstance(cx, thisObj, args.get(0), &isInstance)) {
+    return false;
+  }
+  args.rval().setBoolean(isInstance);
+  return true;
+}
+
+using CheckInstanceFallback = bool (*)(JSContext* cx, JS::CallArgs& args);
+
+static bool InterfaceCheckInstance(JSContext* cx, unsigned argc, JS::Value* vp,
+                                   CheckInstanceFallback fallback) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  // If the thing we were passed is not an object, return false like
+  // OrdinaryHasInstance does.
+  if (!args.get(0).isObject()) {
+    args.rval().setBoolean(false);
+    return true;
+  }
+
+  // If "this" is not an object, likewise return false (again, like
+  // OrdinaryHasInstance).
+  if (!args.thisv().isObject()) {
+    args.rval().setBoolean(false);
+    return true;
+  }
+
+  // If "this" doesn't have a DOMIfaceAndProtoJSClass, it's not a DOM
+  // constructor, so just fall back.  But note that we should
+  // CheckedUnwrapStatic here, because otherwise we won't get the right answers.
+  // The static version is OK, because we're looking for DOM constructors, which
+  // are not cross-origin objects.
+  JS::Rooted<JSObject*> thisObj(
+      cx, js::CheckedUnwrapStatic(&args.thisv().toObject()));
+  if (!thisObj) {
+    // Just fall back on the normal thing, in case it still happens to work.
+    return fallback(cx, args);
+  }
+
+  const JSClass* thisClass = JS::GetClass(thisObj);
+
+  if (!IsDOMIfaceAndProtoClass(thisClass)) {
+    return fallback(cx, args);
+  }
+
+  const DOMIfaceAndProtoJSClass* clasp =
+      DOMIfaceAndProtoJSClass::FromJSClass(thisClass);
+
+  // If "this" isn't a DOM constructor or is a constructor for an interface
+  // without a prototype, just fall back.
+  if (clasp->mType != eInterface ||
+      clasp->mPrototypeID == prototypes::id::_ID_Count) {
+    return fallback(cx, args);
+  }
+
+  JS::Rooted<JSObject*> instance(cx, &args[0].toObject());
+  const DOMJSClass* domClass = GetDOMClass(
+      js::UncheckedUnwrap(instance, /* stopAtWindowProxy = */ false));
+
+  if (domClass &&
+      domClass->mInterfaceChain[clasp->mDepth] == clasp->mPrototypeID) {
+    args.rval().setBoolean(true);
+    return true;
+  }
+
+  if (IsRemoteObjectProxy(instance, clasp->mPrototypeID)) {
+    args.rval().setBoolean(true);
+    return true;
+  }
+
+  return fallback(cx, args);
+}
+
+bool InterfaceHasInstance(JSContext* cx, unsigned argc, JS::Value* vp) {
+  return InterfaceCheckInstance(cx, argc, vp,
+                                [](JSContext* cx, JS::CallArgs& args) {
+                                  return CallOrdinaryHasInstance(cx, args);
+                                });
+}
+
+bool InterfaceHasInstance(JSContext* cx, int prototypeID, int depth,
+                          JS::Handle<JSObject*> instance, bool* bp) {
+  const DOMJSClass* domClass = GetDOMClass(js::UncheckedUnwrap(instance));
+
+  MOZ_ASSERT(!domClass || prototypeID != prototypes::id::_ID_Count,
+             "Why do we have a hasInstance hook if we don't have a prototype "
+             "ID?");
+
+  *bp = (domClass && domClass->mInterfaceChain[depth] == prototypeID);
+  return true;
+}
+
+bool InterfaceIsInstance(JSContext* cx, unsigned argc, JS::Value* vp) {
+  return InterfaceCheckInstance(cx, argc, vp,
+                                [](JSContext*, JS::CallArgs& args) {
+                                  args.rval().setBoolean(false);
+                                  return true;
+                                });
+}
+
+bool ReportLenientThisUnwrappingFailure(JSContext* cx, JSObject* obj) {
+  JS::Rooted<JSObject*> rootedObj(cx, obj);
+  GlobalObject global(cx, rootedObj);
+  if (global.Failed()) {
+    return false;
+  }
+  nsCOMPtr<nsPIDOMWindowInner> window =
+      do_QueryInterface(global.GetAsSupports());
+  if (window && window->GetDoc()) {
+    window->GetDoc()->WarnOnceAbout(DeprecatedOperations::eLenientThis);
+  }
+  return true;
+}
+
+bool GetContentGlobalForJSImplementedObject(BindingCallContext& cx,
+                                            JS::Handle<JSObject*> obj,
+                                            nsIGlobalObject** globalObj) {
+  // Be very careful to not get tricked here.
+  MOZ_ASSERT(NS_IsMainThread());
+  if (!xpc::AccessCheck::isChrome(JS::GetCompartment(obj))) {
+    MOZ_CRASH("Should have a chrome object here");
+  }
+
+  // Look up the content-side object.
+  JS::Rooted<JS::Value> domImplVal(cx);
+  if (!JS_GetProperty(cx, obj, "__DOM_IMPL__", &domImplVal)) {
+    return false;
+  }
+
+  if (!domImplVal.isObject()) {
+    cx.ThrowErrorMessage<MSG_NOT_OBJECT>("Value");
+    return false;
+  }
+
+  // Go ahead and get the global from it.  GlobalObject will handle
+  // doing unwrapping as needed.
+  GlobalObject global(cx, &domImplVal.toObject());
+  if (global.Failed()) {
+    return false;
+  }
+
+  DebugOnly<nsresult> rv =
+      CallQueryInterface(global.GetAsSupports(), globalObj);
+  MOZ_ASSERT(NS_SUCCEEDED(rv));
+  MOZ_ASSERT(*globalObj);
+  return true;
+}
+
+void ConstructJSImplementation(const char* aContractId,
+                               nsIGlobalObject* aGlobal,
+                               JS::MutableHandle<JSObject*> aObject,
+                               ErrorResult& aRv) {
+  MOZ_ASSERT(NS_IsMainThread());
+
+  // Make sure to divorce ourselves from the calling JS while creating and
+  // initializing the object, so exceptions from that will get reported
+  // properly, since those are never exceptions that a spec wants to be thrown.
+  {
+    AutoNoJSAPI nojsapi;
+
+    nsCOMPtr<nsPIDOMWindowInner> window = do_QueryInterface(aGlobal);
+    if (!window) {
+      aRv.ThrowInvalidStateError("Global is not a Window");
+      return;
+    }
+    if (!window->IsCurrentInnerWindow()) {
+      aRv.ThrowInvalidStateError("Window no longer active");
+      return;
+    }
+
+    // Get the XPCOM component containing the JS implementation.
+    nsresult rv;
+    nsCOMPtr<nsISupports> implISupports = do_CreateInstance(aContractId, &rv);
+    if (!implISupports) {
+      nsPrintfCString msg("Failed to get JS implementation for contract \"%s\"",
+                          aContractId);
+      NS_WARNING(msg.get());
+      aRv.Throw(rv);
+      return;
+    }
+    // Initialize the object, if it implements nsIDOMGlobalPropertyInitializer
+    // and our global is a window.
+    nsCOMPtr<nsIDOMGlobalPropertyInitializer> gpi =
+        do_QueryInterface(implISupports);
+    if (gpi) {
+      JS::Rooted<JS::Value> initReturn(RootingCx());
+      rv = gpi->Init(window, &initReturn);
+      if (NS_FAILED(rv)) {
+        aRv.Throw(rv);
+        return;
+      }
+      // With JS-implemented WebIDL, the return value of init() is not used to
+      // determine if init() failed, so init() should only return undefined. Any
+      // kind of permission or pref checking must happen by adding an attribute
+      // to the WebIDL interface.
+      if (!initReturn.isUndefined()) {
+        MOZ_ASSERT(false,
+                   "The init() method for JS-implemented WebIDL should not "
+                   "return anything");
+        MOZ_CRASH();
+      }
+    }
+    // Extract the JS implementation from the XPCOM object.
+    nsCOMPtr<nsIXPConnectWrappedJS> implWrapped =
+        do_QueryInterface(implISupports, &rv);
+    MOZ_ASSERT(implWrapped, "Failed to get wrapped JS from XPCOM component.");
+    if (!implWrapped) {
+      aRv.Throw(rv);
+      return;
+    }
+    aObject.set(implWrapped->GetJSObject());
+    if (!aObject) {
+      aRv.Throw(NS_ERROR_FAILURE);
+    }
+  }
+}
+
+bool NonVoidByteStringToJsval(JSContext* cx, const nsACString& str,
+                              JS::MutableHandle<JS::Value> rval) {
+  // ByteStrings are not UTF-8 encoded.
+  JSString* jsStr = JS_NewStringCopyN(cx, str.Data(), str.Length());
+  if (!jsStr) {
+    return false;
+  }
+  rval.setString(jsStr);
+  return true;
+}
+
+bool NormalizeUSVString(nsAString& aString) {
+  return EnsureUTF16Validity(aString);
+}
+
+bool NormalizeUSVString(binding_detail::FakeString<char16_t>& aString) {
+  uint32_t upTo = Utf16ValidUpTo(aString);
+  uint32_t len = aString.Length();
+  if (upTo == len) {
+    return true;
+  }
+  // This is the part that's different from EnsureUTF16Validity with an
+  // nsAString& argument, because we don't want to ensure mutability in our
+  // BeginWriting() in the common case and nsAString's EnsureMutable is not
+  // public.  This is a little annoying; I wish we could just share the more or
+  // less identical code!
+  if (!aString.EnsureMutable()) {
+    return false;
+  }
+
+  char16_t* ptr = aString.BeginWriting();
+  auto span = Span(ptr, len);
+  span[upTo] = 0xFFFD;
+  EnsureUtf16ValiditySpan(span.From(upTo + 1));
+  return true;
+}
+
+bool ConvertJSValueToByteString(BindingCallContext& cx, JS::Handle<JS::Value> v,
+                                bool nullable, const char* sourceDescription,
+                                nsACString& result) {
+  JS::Rooted<JSString*> s(cx);
+  if (v.isString()) {
+    s = v.toString();
+  } else {
+    if (nullable && v.isNullOrUndefined()) {
+      result.SetIsVoid(true);
+      return true;
+    }
+
+    s = JS::ToString(cx, v);
+    if (!s) {
+      return false;
+    }
+  }
+
+  // Conversion from Javascript string to ByteString is only valid if all
+  // characters < 256. This is always the case for Latin1 strings.
+  size_t length;
+  if (!JS::StringHasLatin1Chars(s)) {
+    // ThrowErrorMessage can GC, so we first scan the string for bad chars
+    // and report the error outside the AutoCheckCannotGC scope.
+    bool foundBadChar = false;
+    size_t badCharIndex;
+    char16_t badChar;
+    {
+      JS::AutoCheckCannotGC nogc;
+      const char16_t* chars =
+          JS_GetTwoByteStringCharsAndLength(cx, nogc, s, &length);
+      if (!chars) {
+        return false;
+      }
+
+      for (size_t i = 0; i < length; i++) {
+        if (chars[i] > 255) {
+          badCharIndex = i;
+          badChar = chars[i];
+          foundBadChar = true;
+          break;
+        }
+      }
+    }
+
+    if (foundBadChar) {
+      MOZ_ASSERT(badCharIndex < length);
+      MOZ_ASSERT(badChar > 255);
+      // The largest unsigned 64 bit number (18,446,744,073,709,551,615) has
+      // 20 digits, plus one more for the null terminator.
+      char index[21];
+      static_assert(sizeof(size_t) <= 8, "index array too small");
+      SprintfLiteral(index, "%zu", badCharIndex);
+      // A char16_t is 16 bits long.  The biggest unsigned 16 bit
+      // number (65,535) has 5 digits, plus one more for the null
+      // terminator.
+      char badCharArray[6];
+      static_assert(sizeof(char16_t) <= 2, "badCharArray too small");
+      SprintfLiteral(badCharArray, "%d", badChar);
+      cx.ThrowErrorMessage<MSG_INVALID_BYTESTRING>(sourceDescription, index,
+                                                   badCharArray);
+      return false;
+    }
+  } else {
+    length = JS::GetStringLength(s);
+  }
+
+  static_assert(JS::MaxStringLength < UINT32_MAX,
+                "length+1 shouldn't overflow");
+
+  if (!result.SetLength(length, fallible)) {
+    return false;
+  }
+
+  if (!JS_EncodeStringToBuffer(cx, s, result.BeginWriting(), length)) {
+    return false;
+  }
+
+  return true;
+}
+
+void FinalizeGlobal(JS::GCContext* aGcx, JSObject* aObj) {
+  MOZ_ASSERT(JS::GetClass(aObj)->flags & JSCLASS_DOM_GLOBAL);
+  mozilla::dom::DestroyProtoAndIfaceCache(aObj);
+}
+
+bool ResolveGlobal(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                   JS::Handle<jsid> aId, bool* aResolvedp) {
+  MOZ_ASSERT(JS_IsGlobalObject(aObj),
+             "Should have a global here, since we plan to resolve standard "
+             "classes!");
+
+  return JS_ResolveStandardClass(aCx, aObj, aId, aResolvedp);
+}
+
+bool MayResolveGlobal(const JSAtomState& aNames, jsid aId,
+                      JSObject* aMaybeObj) {
+  return JS_MayResolveStandardClass(aNames, aId, aMaybeObj);
+}
+
+bool EnumerateGlobal(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                     JS::MutableHandleVector<jsid> aProperties,
+                     bool aEnumerableOnly) {
+  MOZ_ASSERT(JS_IsGlobalObject(aObj),
+             "Should have a global here, since we plan to enumerate standard "
+             "classes!");
+
+  return JS_NewEnumerateStandardClasses(aCx, aObj, aProperties,
+                                        aEnumerableOnly);
+}
+
+bool IsNonExposedGlobal(JSContext* aCx, JSObject* aGlobal,
+                        uint32_t aNonExposedGlobals) {
+  MOZ_ASSERT(aNonExposedGlobals, "Why did we get called?");
+  MOZ_ASSERT((aNonExposedGlobals &
+              ~(GlobalNames::Window | GlobalNames::DedicatedWorkerGlobalScope |
+                GlobalNames::SharedWorkerGlobalScope |
+                GlobalNames::ServiceWorkerGlobalScope |
+                GlobalNames::WorkerDebuggerGlobalScope |
+                GlobalNames::AudioWorkletGlobalScope |
+                GlobalNames::PaintWorkletGlobalScope |
+                GlobalNames::ShadowRealmGlobalScope)) == 0,
+             "Unknown non-exposed global type");
+
+  const char* name = JS::GetClass(aGlobal)->name;
+
+  if ((aNonExposedGlobals & GlobalNames::Window) &&
+      (!strcmp(name, "Window") || !strcmp(name, "BackstagePass"))) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::DedicatedWorkerGlobalScope) &&
+      !strcmp(name, "DedicatedWorkerGlobalScope")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::SharedWorkerGlobalScope) &&
+      !strcmp(name, "SharedWorkerGlobalScope")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::ServiceWorkerGlobalScope) &&
+      !strcmp(name, "ServiceWorkerGlobalScope")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::WorkerDebuggerGlobalScope) &&
+      !strcmp(name, "WorkerDebuggerGlobalScopex")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::AudioWorkletGlobalScope) &&
+      !strcmp(name, "AudioWorkletGlobalScope")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::PaintWorkletGlobalScope) &&
+      !strcmp(name, "PaintWorkletGlobalScope")) {
+    return true;
+  }
+
+  if ((aNonExposedGlobals & GlobalNames::ShadowRealmGlobalScope) &&
+      !strcmp(name, "ShadowRealmGlobalScope")) {
+    return true;
+  }
+
+  return false;
+}
+
+namespace binding_detail {
+
+/**
+ * A ThisPolicy struct needs to provide the following methods:
+ *
+ * HasValidThisValue: Takes a CallArgs and returns a boolean indicating whether
+ *                    the thisv() is valid in the sense of being the right type
+ *                    of Value.  It does not check whether it's the right sort
+ *                    of object if the Value is a JSObject*.
+ *
+ * ExtractThisObject: Takes a CallArgs for which HasValidThisValue was true and
+ *                    returns the JSObject* to use for getting |this|.
+ *
+ * MaybeUnwrapThisObject: If our |this| is a JSObject* that this policy wants to
+ *                        allow unchecked access to for this
+ *                        getter/setter/method, unwrap it.  Otherwise just
+ *                        return the given object.
+ *
+ * UnwrapThisObject: Takes a MutableHandle for a JSObject which contains the
+ *                   this object (which the caller probably got from
+ *                   MaybeUnwrapThisObject). It will try to get the right native
+ *                   out of aObj. In some cases there are 2 possible types for
+ *                   the native (which is why aSelf is a reference to a void*).
+ *                   The ThisPolicy user should use the this JSObject* to
+ *                   determine what C++ class aSelf contains. aObj is used to
+ *                   keep the reflector object alive while self is being used,
+ *                   so its value before and after the UnwrapThisObject call
+ *                   could be different (if aObj was wrapped). The return value
+ *                   is an nsresult, which will signal if an error occurred.
+ *
+ *                   This is passed a JSContext for dynamic unwrapping purposes,
+ *                   but should not throw exceptions on that JSContext.
+ *
+ * HandleInvalidThis: If the |this| is not valid (wrong type of value, wrong
+ *                    object, etc), decide what to do about it.  Returns a
+ *                    boolean to return from the JSNative (false for failure,
+ *                    true for succcess).
+ */
+struct NormalThisPolicy {
+  // This needs to be inlined because it's called on no-exceptions fast-paths.
+  static MOZ_ALWAYS_INLINE bool HasValidThisValue(const JS::CallArgs& aArgs) {
+    // Per WebIDL spec, all getters/setters/methods allow null/undefined "this"
+    // and coerce it to the global.  Then the "is this the right interface?"
+    // check fails if the interface involved is not one that the global
+    // implements.
+    //
+    // As an optimization, we skip doing the null/undefined stuff if we know our
+    // interface is not implemented by the global.
+    return aArgs.thisv().isObject();
+  }
+
+  static MOZ_ALWAYS_INLINE JSObject* ExtractThisObject(
+      const JS::CallArgs& aArgs) {
+    return &aArgs.thisv().toObject();
+  }
+
+  static MOZ_ALWAYS_INLINE JSObject* MaybeUnwrapThisObject(JSObject* aObj) {
+    return aObj;
+  }
+
+  static MOZ_ALWAYS_INLINE nsresult UnwrapThisObject(
+      JS::MutableHandle<JSObject*> aObj, JSContext* aCx, void*& aSelf,
+      prototypes::ID aProtoID, uint32_t aProtoDepth) {
+    binding_detail::MutableObjectHandleWrapper wrapper(aObj);
+    return binding_detail::UnwrapObjectInternal<void, true>(
+        wrapper, aSelf, aProtoID, aProtoDepth, aCx);
+  }
+
+  static bool HandleInvalidThis(JSContext* aCx, const JS::CallArgs& aArgs,
+                                bool aSecurityError, prototypes::ID aProtoId) {
+    return ThrowInvalidThis(aCx, aArgs, aSecurityError, aProtoId);
+  }
+};
+
+struct MaybeGlobalThisPolicy : public NormalThisPolicy {
+  static MOZ_ALWAYS_INLINE bool HasValidThisValue(const JS::CallArgs& aArgs) {
+    // Here we have to allow null/undefined.
+    return aArgs.thisv().isObject() || aArgs.thisv().isNullOrUndefined();
+  }
+
+  static MOZ_ALWAYS_INLINE JSObject* ExtractThisObject(
+      const JS::CallArgs& aArgs) {
+    return aArgs.thisv().isObject()
+               ? &aArgs.thisv().toObject()
+               : JS::GetNonCCWObjectGlobal(&aArgs.callee());
+  }
+
+  // We want the MaybeUnwrapThisObject of NormalThisPolicy.
+
+  // We want the HandleInvalidThis of NormalThisPolicy.
+};
+
+// Shared LenientThis behavior for our two different LenientThis policies.
+struct LenientThisPolicyMixin {
+  static bool HandleInvalidThis(JSContext* aCx, const JS::CallArgs& aArgs,
+                                bool aSecurityError, prototypes::ID aProtoId) {
+    if (aSecurityError) {
+      return NormalThisPolicy::HandleInvalidThis(aCx, aArgs, aSecurityError,
+                                                 aProtoId);
+    }
+
+    MOZ_ASSERT(!JS_IsExceptionPending(aCx));
+    if (!ReportLenientThisUnwrappingFailure(aCx, &aArgs.callee())) {
+      return false;
+    }
+    aArgs.rval().set(JS::UndefinedValue());
+    return true;
+  }
+};
+
+// There are some LenientThis things on globals, so we inherit from
+// MaybeGlobalThisPolicy.
+struct LenientThisPolicy : public MaybeGlobalThisPolicy,
+                           public LenientThisPolicyMixin {
+  // We want the HasValidThisValue of MaybeGlobalThisPolicy.
+
+  // We want the ExtractThisObject of MaybeGlobalThisPolicy.
+
+  // We want the MaybeUnwrapThisObject of MaybeGlobalThisPolicy.
+
+  // We want HandleInvalidThis from LenientThisPolicyMixin
+  using LenientThisPolicyMixin::HandleInvalidThis;
+};
+
+// There are some cross-origin things on globals, so we inherit from
+// MaybeGlobalThisPolicy.
+struct CrossOriginThisPolicy : public MaybeGlobalThisPolicy {
+  // We want the HasValidThisValue of MaybeGlobalThisPolicy.
+
+  // We want the ExtractThisObject of MaybeGlobalThisPolicy.
+
+  static MOZ_ALWAYS_INLINE JSObject* MaybeUnwrapThisObject(JSObject* aObj) {
+    if (xpc::WrapperFactory::IsCrossOriginWrapper(aObj)) {
+      return js::UncheckedUnwrap(aObj);
+    }
+
+    // Else just return aObj; our UnwrapThisObject call will try to
+    // CheckedUnwrap it, and either succeed or get a security error as needed.
+    return aObj;
+  }
+
+  // After calling UnwrapThisObject aSelf can contain one of 2 types, depending
+  // on whether aObj is a proxy with a RemoteObjectProxy handler or a (maybe
+  // wrapped) normal WebIDL reflector. The generated binding code relies on this
+  // and uses IsRemoteObjectProxy to determine what type aSelf points to.
+  static MOZ_ALWAYS_INLINE nsresult UnwrapThisObject(
+      JS::MutableHandle<JSObject*> aObj, JSContext* aCx, void*& aSelf,
+      prototypes::ID aProtoID, uint32_t aProtoDepth) {
+    binding_detail::MutableObjectHandleWrapper wrapper(aObj);
+    // We need to pass false here, because if aObj doesn't have a DOMJSClass
+    // it might be a remote proxy object, and we don't want to throw in that
+    // case (even though unwrapping would fail).
+    nsresult rv = binding_detail::UnwrapObjectInternal<void, false>(
+        wrapper, aSelf, aProtoID, aProtoDepth, nullptr);
+    if (NS_SUCCEEDED(rv)) {
+      return rv;
+    }
+
+    if (js::IsWrapper(wrapper)) {
+      // We want CheckedUnwrapDynamic here: aCx represents the Realm we are in
+      // right now, so we want to check whether that Realm should be able to
+      // access the object.  And this object can definitely be a WindowProxy, so
+      // we need he dynamic check.
+      JSObject* unwrappedObj = js::CheckedUnwrapDynamic(
+          wrapper, aCx, /* stopAtWindowProxy = */ false);
+      if (!unwrappedObj) {
+        return NS_ERROR_XPC_SECURITY_MANAGER_VETO;
+      }
+
+      // At this point we want to keep "unwrappedObj" alive, because we don't
+      // hold a strong reference in "aSelf".
+      wrapper = unwrappedObj;
+
+      return binding_detail::UnwrapObjectInternal<void, false>(
+          wrapper, aSelf, aProtoID, aProtoDepth, nullptr);
+    }
+
+    if (!IsRemoteObjectProxy(wrapper, aProtoID)) {
+      return NS_ERROR_XPC_BAD_CONVERT_JS;
+    }
+    aSelf = RemoteObjectProxyBase::GetNative(wrapper);
+    return NS_OK;
+  }
+
+  // We want the HandleInvalidThis of MaybeGlobalThisPolicy.
+};
+
+// Some objects that can be cross-origin objects are globals, so we inherit
+// from MaybeGlobalThisPolicy.
+struct MaybeCrossOriginObjectThisPolicy : public MaybeGlobalThisPolicy {
+  // We want the HasValidThisValue of MaybeGlobalThisPolicy.
+
+  // We want the ExtractThisObject of MaybeGlobalThisPolicy.
+
+  // We want the MaybeUnwrapThisObject of MaybeGlobalThisPolicy
+
+  static MOZ_ALWAYS_INLINE nsresult UnwrapThisObject(
+      JS::MutableHandle<JSObject*> aObj, JSContext* aCx, void*& aSelf,
+      prototypes::ID aProtoID, uint32_t aProtoDepth) {
+    // There are two cases at this point: either aObj is a cross-compartment
+    // wrapper (CCW) or it's not.  If it is, we don't need to do anything
+    // special compared to MaybeGlobalThisPolicy: the CCW will do the relevant
+    // security checks.  Which is good, because if we tried to do the
+    // cross-origin object check _before_ unwrapping it would always come back
+    // as "same-origin" and if we tried to do it after unwrapping it would be
+    // completely wrong: the checks rely on the two sides of the comparison
+    // being symmetric (can access each other or cannot access each other), but
+    // if we have a CCW we could have an Xray, which is asymmetric.  And then
+    // we'd think we should deny access, whereas we should actually allow
+    // access.
+    //
+    // If we do _not_ have a CCW here, then we need to check whether it's a
+    // cross-origin-accessible object, and if it is check whether it's
+    // same-origin-domain with our current callee.
+    if (!js::IsCrossCompartmentWrapper(aObj) &&
+        xpc::IsCrossOriginAccessibleObject(aObj) &&
+        !MaybeCrossOriginObjectMixins::IsPlatformObjectSameOrigin(aCx, aObj)) {
+      return NS_ERROR_XPC_SECURITY_MANAGER_VETO;
+    }
+
+    return MaybeGlobalThisPolicy::UnwrapThisObject(aObj, aCx, aSelf, aProtoID,
+                                                   aProtoDepth);
+  }
+
+  // We want the HandleInvalidThis of MaybeGlobalThisPolicy.
+};
+
+// And in some cases we are dealing with a maybe-cross-origin object _and_ need
+// [LenientThis] behavior.
+struct MaybeCrossOriginObjectLenientThisPolicy
+    : public MaybeCrossOriginObjectThisPolicy,
+      public LenientThisPolicyMixin {
+  // We want to get all of our behavior from
+  // MaybeCrossOriginObjectLenientThisPolicy, except for HandleInvalidThis,
+  // which should come from LenientThisPolicyMixin.
+  using LenientThisPolicyMixin::HandleInvalidThis;
+};
+
+/**
+ * An ExceptionPolicy struct provides a single HandleException method which is
+ * used to handle an exception, if any.  The method is given the current
+ * success/failure boolean so it can decide whether there is in fact an
+ * exception involved.
+ */
+struct ThrowExceptions {
+  // This needs to be inlined because it's called even on no-exceptions
+  // fast-paths.
+  static MOZ_ALWAYS_INLINE bool HandleException(JSContext* aCx,
+                                                JS::CallArgs& aArgs,
+                                                const JSJitInfo* aInfo,
+                                                bool aOK) {
+    return aOK;
+  }
+};
+
+struct ConvertExceptionsToPromises {
+  // This needs to be inlined because it's called even on no-exceptions
+  // fast-paths.
+  static MOZ_ALWAYS_INLINE bool HandleException(JSContext* aCx,
+                                                JS::CallArgs& aArgs,
+                                                const JSJitInfo* aInfo,
+                                                bool aOK) {
+    // Promise-returning getters/methods always return objects.
+    MOZ_ASSERT(aInfo->returnType() == JSVAL_TYPE_OBJECT);
+
+    if (aOK) {
+      return true;
+    }
+
+    return ConvertExceptionToPromise(aCx, aArgs.rval());
+  }
+};
+
+template <typename ThisPolicy, typename ExceptionPolicy>
+bool GenericGetter(JSContext* cx, unsigned argc, JS::Value* vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  prototypes::ID protoID = static_cast<prototypes::ID>(info->protoID);
+  if (!ThisPolicy::HasValidThisValue(args)) {
+    bool ok = ThisPolicy::HandleInvalidThis(cx, args, false, protoID);
+    return ExceptionPolicy::HandleException(cx, args, info, ok);
+  }
+  JS::Rooted<JSObject*> obj(cx, ThisPolicy::ExtractThisObject(args));
+
+  // NOTE: we want to leave obj in its initial compartment, so don't want to
+  // pass it to UnwrapObjectInternal.  Also, the thing we pass to
+  // UnwrapObjectInternal may be affected by our ThisPolicy.
+  JS::Rooted<JSObject*> rootSelf(cx, ThisPolicy::MaybeUnwrapThisObject(obj));
+  void* self;
+  {
+    nsresult rv =
+        ThisPolicy::UnwrapThisObject(&rootSelf, cx, self, protoID, info->depth);
+    if (NS_FAILED(rv)) {
+      bool ok = ThisPolicy::HandleInvalidThis(
+          cx, args, rv == NS_ERROR_XPC_SECURITY_MANAGER_VETO, protoID);
+      return ExceptionPolicy::HandleException(cx, args, info, ok);
+    }
+  }
+
+  MOZ_ASSERT(info->type() == JSJitInfo::Getter);
+  JSJitGetterOp getter = info->getter;
+  bool ok = getter(cx, obj, self, JSJitGetterCallArgs(args));
+#ifdef DEBUG
+  if (ok) {
+    AssertReturnTypeMatchesJitinfo(info, args.rval());
+  }
+#endif
+  return ExceptionPolicy::HandleException(cx, args, info, ok);
+}
+
+// Force instantiation of the specializations of GenericGetter we need here.
+template bool GenericGetter<NormalThisPolicy, ThrowExceptions>(JSContext* cx,
+                                                               unsigned argc,
+                                                               JS::Value* vp);
+template bool GenericGetter<NormalThisPolicy, ConvertExceptionsToPromises>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericGetter<MaybeGlobalThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericGetter<MaybeGlobalThisPolicy, ConvertExceptionsToPromises>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericGetter<LenientThisPolicy, ThrowExceptions>(JSContext* cx,
+                                                                unsigned argc,
+                                                                JS::Value* vp);
+// There aren't any [LenientThis] Promise-returning getters, so don't
+// bother instantiating that specialization.
+template bool GenericGetter<CrossOriginThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+// There aren't any cross-origin Promise-returning getters, so don't
+// bother instantiating that specialization.
+template bool GenericGetter<MaybeCrossOriginObjectThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+// There aren't any maybe-cross-origin-object Promise-returning getters, so
+// don't bother instantiating that specialization.
+template bool GenericGetter<MaybeCrossOriginObjectLenientThisPolicy,
+                            ThrowExceptions>(JSContext* cx, unsigned argc,
+                                             JS::Value* vp);
+// There aren't any maybe-cross-origin-object Promise-returning lenient-this
+// getters, so don't bother instantiating that specialization.
+
+template <typename ThisPolicy>
+bool GenericSetter(JSContext* cx, unsigned argc, JS::Value* vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  prototypes::ID protoID = static_cast<prototypes::ID>(info->protoID);
+  if (!ThisPolicy::HasValidThisValue(args)) {
+    return ThisPolicy::HandleInvalidThis(cx, args, false, protoID);
+  }
+  JS::Rooted<JSObject*> obj(cx, ThisPolicy::ExtractThisObject(args));
+
+  // NOTE: we want to leave obj in its initial compartment, so don't want to
+  // pass it to UnwrapObject.  Also the thing we pass to UnwrapObjectInternal
+  // may be affected by our ThisPolicy.
+  JS::Rooted<JSObject*> rootSelf(cx, ThisPolicy::MaybeUnwrapThisObject(obj));
+  void* self;
+  {
+    nsresult rv =
+        ThisPolicy::UnwrapThisObject(&rootSelf, cx, self, protoID, info->depth);
+    if (NS_FAILED(rv)) {
+      return ThisPolicy::HandleInvalidThis(
+          cx, args, rv == NS_ERROR_XPC_SECURITY_MANAGER_VETO, protoID);
+    }
+  }
+  if (args.length() == 0) {
+    return ThrowNoSetterArg(cx, args, protoID);
+  }
+  MOZ_ASSERT(info->type() == JSJitInfo::Setter);
+  JSJitSetterOp setter = info->setter;
+  if (!setter(cx, obj, self, JSJitSetterCallArgs(args))) {
+    return false;
+  }
+  args.rval().setUndefined();
+#ifdef DEBUG
+  AssertReturnTypeMatchesJitinfo(info, args.rval());
+#endif
+  return true;
+}
+
+// Force instantiation of the specializations of GenericSetter we need here.
+template bool GenericSetter<NormalThisPolicy>(JSContext* cx, unsigned argc,
+                                              JS::Value* vp);
+template bool GenericSetter<MaybeGlobalThisPolicy>(JSContext* cx, unsigned argc,
+                                                   JS::Value* vp);
+template bool GenericSetter<LenientThisPolicy>(JSContext* cx, unsigned argc,
+                                               JS::Value* vp);
+template bool GenericSetter<CrossOriginThisPolicy>(JSContext* cx, unsigned argc,
+                                                   JS::Value* vp);
+template bool GenericSetter<MaybeCrossOriginObjectThisPolicy>(JSContext* cx,
+                                                              unsigned argc,
+                                                              JS::Value* vp);
+template bool GenericSetter<MaybeCrossOriginObjectLenientThisPolicy>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+
+template <typename ThisPolicy, typename ExceptionPolicy>
+bool GenericMethod(JSContext* cx, unsigned argc, JS::Value* vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  prototypes::ID protoID = static_cast<prototypes::ID>(info->protoID);
+  if (!ThisPolicy::HasValidThisValue(args)) {
+    bool ok = ThisPolicy::HandleInvalidThis(cx, args, false, protoID);
+    return ExceptionPolicy::HandleException(cx, args, info, ok);
+  }
+  JS::Rooted<JSObject*> obj(cx, ThisPolicy::ExtractThisObject(args));
+
+  // NOTE: we want to leave obj in its initial compartment, so don't want to
+  // pass it to UnwrapObjectInternal.  Also, the thing we pass to
+  // UnwrapObjectInternal may be affected by our ThisPolicy.
+  JS::Rooted<JSObject*> rootSelf(cx, ThisPolicy::MaybeUnwrapThisObject(obj));
+  void* self;
+  {
+    nsresult rv =
+        ThisPolicy::UnwrapThisObject(&rootSelf, cx, self, protoID, info->depth);
+    if (NS_FAILED(rv)) {
+      bool ok = ThisPolicy::HandleInvalidThis(
+          cx, args, rv == NS_ERROR_XPC_SECURITY_MANAGER_VETO, protoID);
+      return ExceptionPolicy::HandleException(cx, args, info, ok);
+    }
+  }
+  MOZ_ASSERT(info->type() == JSJitInfo::Method);
+  JSJitMethodOp method = info->method;
+  bool ok = method(cx, obj, self, JSJitMethodCallArgs(args));
+#ifdef DEBUG
+  if (ok) {
+    AssertReturnTypeMatchesJitinfo(info, args.rval());
+  }
+#endif
+  return ExceptionPolicy::HandleException(cx, args, info, ok);
+}
+
+// Force instantiation of the specializations of GenericMethod we need here.
+template bool GenericMethod<NormalThisPolicy, ThrowExceptions>(JSContext* cx,
+                                                               unsigned argc,
+                                                               JS::Value* vp);
+template bool GenericMethod<NormalThisPolicy, ConvertExceptionsToPromises>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericMethod<MaybeGlobalThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericMethod<MaybeGlobalThisPolicy, ConvertExceptionsToPromises>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericMethod<CrossOriginThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+// There aren't any cross-origin Promise-returning methods, so don't
+// bother instantiating that specialization.
+template bool GenericMethod<MaybeCrossOriginObjectThisPolicy, ThrowExceptions>(
+    JSContext* cx, unsigned argc, JS::Value* vp);
+template bool GenericMethod<MaybeCrossOriginObjectThisPolicy,
+                            ConvertExceptionsToPromises>(JSContext* cx,
+                                                         unsigned argc,
+                                                         JS::Value* vp);
+
+}  // namespace binding_detail
+
+bool StaticMethodPromiseWrapper(JSContext* cx, unsigned argc, JS::Value* vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+
+  const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+  MOZ_ASSERT(info);
+  MOZ_ASSERT(info->type() == JSJitInfo::StaticMethod);
+
+  bool ok = info->staticMethod(cx, argc, vp);
+  if (ok) {
+    return true;
+  }
+
+  return ConvertExceptionToPromise(cx, args.rval());
+}
+
+bool ConvertExceptionToPromise(JSContext* cx,
+                               JS::MutableHandle<JS::Value> rval) {
+  JS::Rooted<JS::Value> exn(cx);
+  if (!JS_GetPendingException(cx, &exn)) {
+    // This is very important: if there is no pending exception here but we're
+    // ending up in this code, that means the callee threw an uncatchable
+    // exception.  Just propagate that out as-is.
+    return false;
+  }
+
+  JS_ClearPendingException(cx);
+
+  JSObject* promise = JS::CallOriginalPromiseReject(cx, exn);
+  if (!promise) {
+    // We just give up.  Put the exception back.
+    JS_SetPendingException(cx, exn);
+    return false;
+  }
+
+  rval.setObject(*promise);
+  return true;
+}
+
+/* static */
+void CreateGlobalOptionsWithXPConnect::TraceGlobal(JSTracer* aTrc,
+                                                   JSObject* aObj) {
+  xpc::TraceXPCGlobal(aTrc, aObj);
+}
+
+/* static */
+bool CreateGlobalOptionsWithXPConnect::PostCreateGlobal(
+    JSContext* aCx, JS::Handle<JSObject*> aGlobal) {
+  JSPrincipals* principals =
+      JS::GetRealmPrincipals(js::GetNonCCWObjectRealm(aGlobal));
+  nsIPrincipal* principal = nsJSPrincipals::get(principals);
+
+  SiteIdentifier site;
+  nsresult rv = BasePrincipal::Cast(principal)->GetSiteIdentifier(site);
+  NS_ENSURE_SUCCESS(rv, false);
+
+  xpc::RealmPrivate::Init(aGlobal, site);
+  return true;
+}
+
+uint64_t GetWindowID(void* aGlobal) { return 0; }
+
+uint64_t GetWindowID(nsGlobalWindowInner* aGlobal) {
+  return aGlobal->WindowID();
+}
+
+uint64_t GetWindowID(DedicatedWorkerGlobalScope* aGlobal) {
+  return aGlobal->WindowID();
+}
+
+#ifdef DEBUG
+void AssertReturnTypeMatchesJitinfo(const JSJitInfo* aJitInfo,
+                                    JS::Handle<JS::Value> aValue) {
+  switch (aJitInfo->returnType()) {
+    case JSVAL_TYPE_UNKNOWN:
+      // Any value is good.
+      break;
+    case JSVAL_TYPE_DOUBLE:
+      // The value could actually be an int32 value as well.
+      MOZ_ASSERT(aValue.isNumber());
+      break;
+    case JSVAL_TYPE_INT32:
+      MOZ_ASSERT(aValue.isInt32());
+      break;
+    case JSVAL_TYPE_UNDEFINED:
+      MOZ_ASSERT(aValue.isUndefined());
+      break;
+    case JSVAL_TYPE_BOOLEAN:
+      MOZ_ASSERT(aValue.isBoolean());
+      break;
+    case JSVAL_TYPE_STRING:
+      MOZ_ASSERT(aValue.isString());
+      break;
+    case JSVAL_TYPE_NULL:
+      MOZ_ASSERT(aValue.isNull());
+      break;
+    case JSVAL_TYPE_OBJECT:
+      MOZ_ASSERT(aValue.isObject());
+      break;
+    default:
+      // Someone messed up their jitinfo type.
+      MOZ_ASSERT(false, "Unexpected JSValueType stored in jitinfo");
+      break;
+  }
+}
+#endif
+
+bool CallerSubsumes(JSObject* aObject) {
+  // Remote object proxies are not CCWs, so unwrapping them does not get you
+  // their "real" principal, but we want to treat them like cross-origin objects
+  // when considering them as WebIDL arguments, for consistency.
+  if (IsRemoteObjectProxy(aObject)) {
+    return false;
+  }
+  nsIPrincipal* objPrin =
+      nsContentUtils::ObjectPrincipal(js::UncheckedUnwrap(aObject));
+  return nsContentUtils::SubjectPrincipal()->Subsumes(objPrin);
+}
+
+nsresult UnwrapArgImpl(JSContext* cx, JS::Handle<JSObject*> src,
+                       const nsIID& iid, void** ppArg) {
+  if (!NS_IsMainThread()) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  // The JSContext represents the "who is unwrapping" realm, so we want to use
+  // it for ReflectorToISupportsDynamic here.
+  nsCOMPtr<nsISupports> iface = xpc::ReflectorToISupportsDynamic(src, cx);
+  if (iface) {
+    if (NS_FAILED(iface->QueryInterface(iid, ppArg))) {
+      return NS_ERROR_XPC_BAD_CONVERT_JS;
+    }
+
+    return NS_OK;
+  }
+
+  // Only allow XPCWrappedJS stuff in system code.  Ideally we would remove this
+  // even there, but that involves converting some things to WebIDL callback
+  // interfaces and making some other things builtinclass...
+  if (!nsContentUtils::IsSystemCaller(cx)) {
+    return NS_ERROR_XPC_BAD_CONVERT_JS;
+  }
+
+  RefPtr<nsXPCWrappedJS> wrappedJS;
+  nsresult rv =
+      nsXPCWrappedJS::GetNewOrUsed(cx, src, iid, getter_AddRefs(wrappedJS));
+  if (NS_FAILED(rv) || !wrappedJS) {
+    return rv;
+  }
+
+  // We need to go through the QueryInterface logic to make this return
+  // the right thing for the various 'special' interfaces; e.g.
+  // nsIPropertyBag. We must use AggregatedQueryInterface in cases where
+  // there is an outer to avoid nasty recursion.
+  return wrappedJS->QueryInterface(iid, ppArg);
+}
+
+nsresult UnwrapWindowProxyArg(JSContext* cx, JS::Handle<JSObject*> src,
+                              WindowProxyHolder& ppArg) {
+  if (IsRemoteObjectProxy(src, prototypes::id::Window)) {
+    ppArg =
+        static_cast<BrowsingContext*>(RemoteObjectProxyBase::GetNative(src));
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsPIDOMWindowInner> inner;
+  nsresult rv = UnwrapArg<nsPIDOMWindowInner>(cx, src, getter_AddRefs(inner));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsPIDOMWindowOuter> outer = inner->GetOuterWindow();
+  RefPtr<BrowsingContext> bc = outer ? outer->GetBrowsingContext() : nullptr;
+  ppArg = std::move(bc);
+  return NS_OK;
+}
+
+template <auto Method, typename... Args>
+static bool GetBackingObject(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                             size_t aSlotIndex,
+                             JS::MutableHandle<JSObject*> aBackingObj,
+                             bool* aBackingObjCreated, Args... aArgs) {
+  JS::Rooted<JSObject*> reflector(aCx);
+  reflector = IsDOMObject(aObj)
+                  ? aObj
+                  : js::UncheckedUnwrap(aObj,
+                                        /* stopAtWindowProxy = */ false);
+
+  // Retrieve the backing object from the reserved slot on the maplike/setlike
+  // object. If it doesn't exist yet, create it.
+  JS::Rooted<JS::Value> slotValue(aCx);
+  slotValue = JS::GetReservedSlot(reflector, aSlotIndex);
+  if (slotValue.isUndefined()) {
+    // Since backing object access can happen in non-originating realms,
+    // make sure to create the backing object in reflector realm.
+    {
+      JSAutoRealm ar(aCx, reflector);
+      JS::Rooted<JSObject*> newBackingObj(aCx);
+      newBackingObj.set(Method(aCx, aArgs...));
+      if (NS_WARN_IF(!newBackingObj)) {
+        return false;
+      }
+      JS::SetReservedSlot(reflector, aSlotIndex,
+                          JS::ObjectValue(*newBackingObj));
+    }
+    slotValue = JS::GetReservedSlot(reflector, aSlotIndex);
+    *aBackingObjCreated = true;
+  } else {
+    *aBackingObjCreated = false;
+  }
+  if (!MaybeWrapNonDOMObjectValue(aCx, &slotValue)) {
+    return false;
+  }
+  aBackingObj.set(&slotValue.toObject());
+  return true;
+}
+
+bool GetMaplikeBackingObject(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                             size_t aSlotIndex,
+                             JS::MutableHandle<JSObject*> aBackingObj,
+                             bool* aBackingObjCreated) {
+  return GetBackingObject<JS::NewMapObject>(aCx, aObj, aSlotIndex, aBackingObj,
+                                            aBackingObjCreated);
+}
+
+bool GetSetlikeBackingObject(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                             size_t aSlotIndex,
+                             JS::MutableHandle<JSObject*> aBackingObj,
+                             bool* aBackingObjCreated) {
+  return GetBackingObject<JS::NewSetObject>(aCx, aObj, aSlotIndex, aBackingObj,
+                                            aBackingObjCreated);
+}
+
+static inline JSObject* NewObservableArrayProxyObject(
+    JSContext* aCx, const ObservableArrayProxyHandler* aHandler, void* aOwner) {
+  JS::Rooted<JSObject*> target(aCx, JS::NewArrayObject(aCx, 0));
+  if (NS_WARN_IF(!target)) {
+    return nullptr;
+  }
+
+  JS::Rooted<JS::Value> targetValue(aCx, JS::ObjectValue(*target));
+  JS::Rooted<JSObject*> proxy(
+      aCx, js::NewProxyObject(aCx, aHandler, targetValue, nullptr));
+  if (!proxy) {
+    return nullptr;
+  }
+  js::SetProxyReservedSlot(proxy, OBSERVABLE_ARRAY_DOM_INTERFACE_SLOT,
+                           JS::PrivateValue(aOwner));
+  return proxy;
+}
+
+bool GetObservableArrayBackingObject(
+    JSContext* aCx, JS::Handle<JSObject*> aObj, size_t aSlotIndex,
+    JS::MutableHandle<JSObject*> aBackingObj, bool* aBackingObjCreated,
+    const ObservableArrayProxyHandler* aHandler, void* aOwner) {
+  return GetBackingObject<NewObservableArrayProxyObject>(
+      aCx, aObj, aSlotIndex, aBackingObj, aBackingObjCreated, aHandler, aOwner);
+}
+
+bool ForEachHandler(JSContext* aCx, unsigned aArgc, JS::Value* aVp) {
+  JS::CallArgs args = CallArgsFromVp(aArgc, aVp);
+  // Unpack callback and object from slots
+  JS::Rooted<JS::Value> callbackFn(
+      aCx,
+      js::GetFunctionNativeReserved(&args.callee(), FOREACH_CALLBACK_SLOT));
+  JS::Rooted<JS::Value> maplikeOrSetlikeObj(
+      aCx, js::GetFunctionNativeReserved(&args.callee(),
+                                         FOREACH_MAPLIKEORSETLIKEOBJ_SLOT));
+  MOZ_ASSERT(aArgc == 3);
+  JS::RootedVector<JS::Value> newArgs(aCx);
+  // Arguments are passed in as value, key, object. Keep value and key, replace
+  // object with the maplike/setlike object.
+  if (!newArgs.append(args.get(0))) {
+    return false;
+  }
+  if (!newArgs.append(args.get(1))) {
+    return false;
+  }
+  if (!newArgs.append(maplikeOrSetlikeObj)) {
+    return false;
+  }
+  JS::Rooted<JS::Value> rval(aCx, JS::UndefinedValue());
+  // Now actually call the user specified callback
+  return JS::Call(aCx, args.thisv(), callbackFn, newArgs, &rval);
+}
+
+static inline prototypes::ID GetProtoIdForNewtarget(
+    JS::Handle<JSObject*> aNewTarget) {
+  const JSClass* newTargetClass = JS::GetClass(aNewTarget);
+  if (IsDOMIfaceAndProtoClass(newTargetClass)) {
+    const DOMIfaceAndProtoJSClass* newTargetIfaceClass =
+        DOMIfaceAndProtoJSClass::FromJSClass(newTargetClass);
+    if (newTargetIfaceClass->mType == eInterface) {
+      return newTargetIfaceClass->mPrototypeID;
+    }
+  } else if (JS_IsNativeFunction(aNewTarget, Constructor)) {
+    return GetNativePropertyHooksFromConstructorFunction(aNewTarget)
+        ->mPrototypeID;
+  }
+
+  return prototypes::id::_ID_Count;
+}
+
+bool GetDesiredProto(JSContext* aCx, const JS::CallArgs& aCallArgs,
+                     prototypes::id::ID aProtoId,
+                     CreateInterfaceObjectsMethod aCreator,
+                     JS::MutableHandle<JSObject*> aDesiredProto) {
+  // This basically implements
+  // https://heycam.github.io/webidl/#internally-create-a-new-object-implementing-the-interface
+  // step 3.
+  MOZ_ASSERT(aCallArgs.isConstructing(), "How did we end up here?");
+
+  // The desired prototype depends on the actual constructor that was invoked,
+  // which is passed to us as the newTarget in the callargs.  We want to do
+  // something akin to the ES6 specification's GetProtototypeFromConstructor (so
+  // get .prototype on the newTarget, with a fallback to some sort of default).
+
+  // First, a fast path for the case when the the constructor is in fact one of
+  // our DOM constructors.  This is safe because on those the "constructor"
+  // property is non-configurable and non-writable, so we don't have to do the
+  // slow JS_GetProperty call.
+  JS::Rooted<JSObject*> newTarget(aCx, &aCallArgs.newTarget().toObject());
+  MOZ_ASSERT(JS::IsCallable(newTarget));
+  JS::Rooted<JSObject*> originalNewTarget(aCx, newTarget);
+  // See whether we have a known DOM constructor here, such that we can take a
+  // fast path.
+  prototypes::ID protoID = GetProtoIdForNewtarget(newTarget);
+  if (protoID == prototypes::id::_ID_Count) {
+    // We might still have a cross-compartment wrapper for a known DOM
+    // constructor.  CheckedUnwrapStatic is fine here, because we're looking for
+    // DOM constructors and those can't be cross-origin objects.
+    newTarget = js::CheckedUnwrapStatic(newTarget);
+    if (newTarget && newTarget != originalNewTarget) {
+      protoID = GetProtoIdForNewtarget(newTarget);
+    }
+  }
+
+  if (protoID != prototypes::id::_ID_Count) {
+    ProtoAndIfaceCache& protoAndIfaceCache =
+        *GetProtoAndIfaceCache(JS::GetNonCCWObjectGlobal(newTarget));
+    aDesiredProto.set(protoAndIfaceCache.EntrySlotMustExist(protoID));
+    if (newTarget != originalNewTarget) {
+      return JS_WrapObject(aCx, aDesiredProto);
+    }
+    return true;
+  }
+
+  // Slow path.  This basically duplicates the ES6 spec's
+  // GetPrototypeFromConstructor except that instead of taking a string naming
+  // the fallback prototype we determine the fallback based on the proto id we
+  // were handed.
+  //
+  // Note that it's very important to do this property get on originalNewTarget,
+  // not our unwrapped newTarget, since we want to get Xray behavior here as
+  // needed.
+  // XXXbz for speed purposes, using a preinterned id here sure would be nice.
+  // We can't use GetJSIDByIndex, because that only works on the main thread,
+  // not workers.
+  JS::Rooted<JS::Value> protoVal(aCx);
+  if (!JS_GetProperty(aCx, originalNewTarget, "prototype", &protoVal)) {
+    return false;
+  }
+
+  if (protoVal.isObject()) {
+    aDesiredProto.set(&protoVal.toObject());
+    return true;
+  }
+
+  // Fall back to getting the proto for our given proto id in the realm that
+  // GetFunctionRealm(newTarget) returns.
+  JS::Rooted<JS::Realm*> realm(aCx, JS::GetFunctionRealm(aCx, newTarget));
+  if (!realm) {
+    return false;
+  }
+
+  {
+    // JS::GetRealmGlobalOrNull should not be returning null here, because we
+    // have live objects in the Realm.
+    JSAutoRealm ar(aCx, JS::GetRealmGlobalOrNull(realm));
+    aDesiredProto.set(
+        GetPerInterfaceObjectHandle(aCx, aProtoId, aCreator, true));
+    if (!aDesiredProto) {
+      return false;
+    }
+  }
+
+  return MaybeWrapObject(aCx, aDesiredProto);
+}
+
+namespace {
+
+class MOZ_RAII AutoConstructionDepth final {
+ public:
+  MOZ_IMPLICIT AutoConstructionDepth(CustomElementDefinition* aDefinition)
+      : mDefinition(aDefinition) {
+    MOZ_ASSERT(mDefinition->mConstructionStack.IsEmpty());
+
+    mDefinition->mConstructionDepth++;
+    // If the mConstructionDepth isn't matched with the length of mPrefixStack,
+    // this means the constructor is called directly from JS, i.e.
+    // 'new CustomElementConstructor()', we have to push a dummy prefix into
+    // stack.
+    if (mDefinition->mConstructionDepth > mDefinition->mPrefixStack.Length()) {
+      mDidPush = true;
+      mDefinition->mPrefixStack.AppendElement(nullptr);
+    }
+
+    MOZ_ASSERT(mDefinition->mConstructionDepth ==
+               mDefinition->mPrefixStack.Length());
+  }
+
+  ~AutoConstructionDepth() {
+    MOZ_ASSERT(mDefinition->mConstructionDepth > 0);
+    MOZ_ASSERT(mDefinition->mConstructionDepth ==
+               mDefinition->mPrefixStack.Length());
+
+    if (mDidPush) {
+      MOZ_ASSERT(mDefinition->mPrefixStack.LastElement() == nullptr);
+      mDefinition->mPrefixStack.RemoveLastElement();
+    }
+    mDefinition->mConstructionDepth--;
+  }
+
+ private:
+  CustomElementDefinition* mDefinition;
+  bool mDidPush = false;
+};
+
+}  // anonymous namespace
+
+// https://html.spec.whatwg.org/multipage/dom.html#htmlconstructor
+namespace binding_detail {
+bool HTMLConstructor(JSContext* aCx, unsigned aArgc, JS::Value* aVp,
+                     constructors::id::ID aConstructorId,
+                     prototypes::id::ID aProtoId,
+                     CreateInterfaceObjectsMethod aCreator) {
+  JS::CallArgs args = JS::CallArgsFromVp(aArgc, aVp);
+
+  // Per spec, this is technically part of step 3, but doing the check
+  // directly lets us provide a better error message.  And then in
+  // step 2 we can work with newTarget in a simpler way because we
+  // know it's an object.
+  if (!args.isConstructing()) {
+    return ThrowConstructorWithoutNew(aCx,
+                                      NamesOfInterfacesWithProtos(aProtoId));
+  }
+
+  JS::Rooted<JSObject*> callee(aCx, &args.callee());
+  // 'callee' is not a function here; it's either an Xray for our interface
+  // object or the interface object itself.  So caling XrayAwareCalleeGlobal on
+  // it is not safe.  But since in the Xray case it's a wrapper for our
+  // interface object, we can just construct our GlobalObject from it and end
+  // up with the right thing.
+  GlobalObject global(aCx, callee);
+  if (global.Failed()) {
+    return false;
+  }
+
+  // Now we start the [HTMLConstructor] algorithm steps from
+  // https://html.spec.whatwg.org/multipage/dom.html#htmlconstructor
+
+  ErrorResult rv;
+  auto scopeExit =
+      MakeScopeExit([&]() { Unused << rv.MaybeSetPendingException(aCx); });
+
+  // Step 1.
+  nsCOMPtr<nsPIDOMWindowInner> window =
+      do_QueryInterface(global.GetAsSupports());
+  if (!window) {
+    // This means we ended up with an HTML Element interface object defined in
+    // a non-Window scope.  That's ... pretty unexpected.
+    rv.Throw(NS_ERROR_UNEXPECTED);
+    return false;
+  }
+  RefPtr<mozilla::dom::CustomElementRegistry> registry(
+      window->CustomElements());
+
+  // Technically, per spec, a window always has a document.  In Gecko, a
+  // sufficiently torn-down window might not, so check for that case.  We're
+  // going to need a document to create an element.
+  Document* doc = window->GetExtantDoc();
+  if (!doc) {
+    rv.Throw(NS_ERROR_UNEXPECTED);
+    return false;
+  }
+
+  // Step 2.
+
+  // The newTarget might be a cross-compartment wrapper. Get the underlying
+  // object so we can do the spec's object-identity checks.  If we ever stop
+  // unwrapping here, carefully audit uses of newTarget below!
+  //
+  // Note that the ES spec enforces that newTarget is always a constructor (in
+  // the sense of having a [[Construct]]), so it's not a cross-origin object and
+  // we can use CheckedUnwrapStatic.
+  JS::Rooted<JSObject*> newTarget(
+      aCx, js::CheckedUnwrapStatic(&args.newTarget().toObject()));
+  if (!newTarget) {
+    rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+    return false;
+  }
+
+  // Enter the compartment of our underlying newTarget object, so we end
+  // up comparing to the constructor object for our interface from that global.
+  // XXXbz This is not what the spec says to do, and it's not super-clear to me
+  // at this point why we're doing it.  Why not just compare |newTarget| and
+  // |callee| if the intent is just to prevent registration of HTML interface
+  // objects as constructors?  Of course it's not clear that the spec check
+  // makes sense to start with: https://github.com/whatwg/html/issues/3575
+  {
+    JSAutoRealm ar(aCx, newTarget);
+    JS::Handle<JSObject*> constructor =
+        GetPerInterfaceObjectHandle(aCx, aConstructorId, aCreator, true);
+    if (!constructor) {
+      return false;
+    }
+    if (newTarget == constructor) {
+      rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+      return false;
+    }
+  }
+
+  // Step 3.
+  CustomElementDefinition* definition =
+      registry->LookupCustomElementDefinition(aCx, newTarget);
+  if (!definition) {
+    rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+    return false;
+  }
+
+  // Steps 4, 5, 6 do some sanity checks on our callee.  We add to those a
+  // determination of what sort of element we're planning to construct.
+  // Technically, this should happen (implicitly) in step 8, but this
+  // determination is side-effect-free, so it's OK.
+  int32_t ns = definition->mNamespaceID;
+
+  constructorGetterCallback cb = nullptr;
+  if (ns == kNameSpaceID_XUL) {
+    if (definition->mLocalName == nsGkAtoms::description ||
+        definition->mLocalName == nsGkAtoms::label) {
+      cb = XULTextElement_Binding::GetConstructorObject;
+    } else if (definition->mLocalName == nsGkAtoms::resizer) {
+      cb = XULResizerElement_Binding::GetConstructorObject;
+    } else if (definition->mLocalName == nsGkAtoms::menupopup ||
+               definition->mLocalName == nsGkAtoms::popup ||
+               definition->mLocalName == nsGkAtoms::panel ||
+               definition->mLocalName == nsGkAtoms::tooltip) {
+      cb = XULPopupElement_Binding::GetConstructorObject;
+    } else if (definition->mLocalName == nsGkAtoms::iframe ||
+               definition->mLocalName == nsGkAtoms::browser ||
+               definition->mLocalName == nsGkAtoms::editor) {
+      cb = XULFrameElement_Binding::GetConstructorObject;
+    } else if (definition->mLocalName == nsGkAtoms::menu ||
+               definition->mLocalName == nsGkAtoms::menulist) {
+      cb = XULMenuElement_Binding::GetConstructorObject;
+    } else if (definition->mLocalName == nsGkAtoms::tree) {
+      cb = XULTreeElement_Binding::GetConstructorObject;
+    } else {
+      cb = XULElement_Binding::GetConstructorObject;
+    }
+  }
+
+  int32_t tag = eHTMLTag_userdefined;
+  if (!definition->IsCustomBuiltIn()) {
+    // Step 4.
+    // If the definition is for an autonomous custom element, the active
+    // function should be HTMLElement or extend from XULElement.
+    if (!cb) {
+      cb = HTMLElement_Binding::GetConstructorObject;
+    }
+
+    // We want to get the constructor from our global's realm, not the
+    // caller realm.
+    JSAutoRealm ar(aCx, global.Get());
+    JS::Rooted<JSObject*> constructor(aCx, cb(aCx));
+
+    // CheckedUnwrapStatic is OK here, since our callee is callable, hence not a
+    // cross-origin object.
+    if (constructor != js::CheckedUnwrapStatic(callee)) {
+      rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+      return false;
+    }
+  } else {
+    if (ns == kNameSpaceID_XHTML) {
+      // Step 5.
+      // If the definition is for a customized built-in element, the localName
+      // should be one of the ones defined in the specification for this
+      // interface.
+      tag = nsHTMLTags::CaseSensitiveAtomTagToId(definition->mLocalName);
+      if (tag == eHTMLTag_userdefined) {
+        rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+        return false;
+      }
+
+      MOZ_ASSERT(tag <= NS_HTML_TAG_MAX, "tag is out of bounds");
+
+      // If the definition is for a customized built-in element, the active
+      // function should be the localname's element interface.
+      cb = sConstructorGetterCallback[tag];
+    }
+
+    if (!cb) {
+      rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+      return false;
+    }
+
+    // We want to get the constructor from our global's realm, not the
+    // caller realm.
+    JSAutoRealm ar(aCx, global.Get());
+    JS::Rooted<JSObject*> constructor(aCx, cb(aCx));
+    if (!constructor) {
+      return false;
+    }
+
+    // CheckedUnwrapStatic is OK here, since our callee is callable, hence not a
+    // cross-origin object.
+    if (constructor != js::CheckedUnwrapStatic(callee)) {
+      rv.ThrowTypeError<MSG_ILLEGAL_CONSTRUCTOR>();
+      return false;
+    }
+  }
+
+  // Steps 7 and 8.
+  JS::Rooted<JSObject*> desiredProto(aCx);
+  if (!GetDesiredProto(aCx, args, aProtoId, aCreator, &desiredProto)) {
+    return false;
+  }
+
+  MOZ_ASSERT(desiredProto, "How could we not have a prototype by now?");
+
+  // We need to do some work to actually return an Element, so we do step 8 on
+  // one branch and steps 9-12 on another branch, then common up the "return
+  // element" work.
+  RefPtr<Element> element;
+  nsTArray<RefPtr<Element>>& constructionStack = definition->mConstructionStack;
+  if (constructionStack.IsEmpty()) {
+    // Step 8.
+    // Now we go to construct an element.  We want to do this in global's
+    // realm, not caller realm (the normal constructor behavior),
+    // just in case those elements create JS things.
+    JSAutoRealm ar(aCx, global.Get());
+    AutoConstructionDepth acd(definition);
+
+    RefPtr<NodeInfo> nodeInfo = doc->NodeInfoManager()->GetNodeInfo(
+        definition->mLocalName, definition->mPrefixStack.LastElement(), ns,
+        nsINode::ELEMENT_NODE);
+    MOZ_ASSERT(nodeInfo);
+
+    if (ns == kNameSpaceID_XUL) {
+      element = nsXULElement::Construct(nodeInfo.forget());
+
+    } else {
+      if (tag == eHTMLTag_userdefined) {
+        // Autonomous custom element.
+        element = NS_NewHTMLElement(nodeInfo.forget());
+      } else {
+        // Customized built-in element.
+        element = CreateHTMLElement(tag, nodeInfo.forget(), NOT_FROM_PARSER);
+      }
+    }
+
+    element->SetCustomElementData(MakeUnique<CustomElementData>(
+        definition->mType, CustomElementData::State::eCustom));
+
+    element->SetCustomElementDefinition(definition);
+  } else {
+    // Step 9.
+    element = constructionStack.LastElement();
+
+    // Step 10.
+    if (element == ALREADY_CONSTRUCTED_MARKER) {
+      rv.ThrowTypeError(
+          "Cannot instantiate a custom element inside its own constructor "
+          "during upgrades");
+      return false;
+    }
+
+    // Step 11.
+    // Do prototype swizzling for upgrading a custom element here, for cases
+    // when we have a reflector already.  If we don't have one yet, we will
+    // create it with the right proto (by calling GetOrCreateDOMReflector with
+    // that proto), and will preserve it by means of the proto != canonicalProto
+    // check).
+    JS::Rooted<JSObject*> reflector(aCx, element->GetWrapper());
+    if (reflector) {
+      // reflector might be in different realm.
+      JSAutoRealm ar(aCx, reflector);
+      JS::Rooted<JSObject*> givenProto(aCx, desiredProto);
+      if (!JS_WrapObject(aCx, &givenProto) ||
+          !JS_SetPrototype(aCx, reflector, givenProto)) {
+        return false;
+      }
+      PreserveWrapper(element.get());
+    }
+
+    // Step 12.
+    constructionStack.LastElement() = ALREADY_CONSTRUCTED_MARKER;
+  }
+
+  // Tail end of step 8 and step 13: returning the element.  We want to do this
+  // part in the global's realm, though in practice it won't matter much
+  // because Element always knows which realm it should be created in.
+  JSAutoRealm ar(aCx, global.Get());
+  if (!js::IsObjectInContextCompartment(desiredProto, aCx) &&
+      !JS_WrapObject(aCx, &desiredProto)) {
+    return false;
+  }
+
+  return GetOrCreateDOMReflector(aCx, element, args.rval(), desiredProto);
+}
+}  // namespace binding_detail
+
+#ifdef DEBUG
+namespace binding_detail {
+void AssertReflectorHasGivenProto(JSContext* aCx, JSObject* aReflector,
+                                  JS::Handle<JSObject*> aGivenProto) {
+  if (!aGivenProto) {
+    // Nothing to assert here
+    return;
+  }
+
+  JS::Rooted<JSObject*> reflector(aCx, aReflector);
+  JSAutoRealm ar(aCx, reflector);
+  JS::Rooted<JSObject*> reflectorProto(aCx);
+  bool ok = JS_GetPrototype(aCx, reflector, &reflectorProto);
+  MOZ_ASSERT(ok);
+  // aGivenProto may not be in the right realm here, so we
+  // have to wrap it to compare.
+  JS::Rooted<JSObject*> givenProto(aCx, aGivenProto);
+  ok = JS_WrapObject(aCx, &givenProto);
+  MOZ_ASSERT(ok);
+  MOZ_ASSERT(givenProto == reflectorProto,
+             "How are we supposed to change the proto now?");
+}
+}  // namespace binding_detail
+#endif  // DEBUG
+
+void SetUseCounter(JSObject* aObject, UseCounter aUseCounter) {
+  nsGlobalWindowInner* win =
+      xpc::WindowGlobalOrNull(js::UncheckedUnwrap(aObject));
+  if (win && win->GetDocument()) {
+    win->GetDocument()->SetUseCounter(aUseCounter);
+  }
+}
+
+void SetUseCounter(UseCounterWorker aUseCounter) {
+  // If this is called from Worklet thread, workerPrivate will be null.
+  WorkerPrivate* workerPrivate = GetCurrentThreadWorkerPrivate();
+  if (workerPrivate) {
+    workerPrivate->SetUseCounter(aUseCounter);
+  }
+}
+
+namespace {
+
+#define DEPRECATED_OPERATION(_op) #_op,
+static const char* kDeprecatedOperations[] = {
+#include "nsDeprecatedOperationList.h"
+    nullptr};
+#undef DEPRECATED_OPERATION
+
+void ReportDeprecation(nsIGlobalObject* aGlobal, nsIURI* aURI,
+                       DeprecatedOperations aOperation,
+                       const nsAString& aFileName,
+                       const Nullable<uint32_t>& aLineNumber,
+                       const Nullable<uint32_t>& aColumnNumber) {
+  MOZ_ASSERT(aURI);
+
+  // If the URI has the data scheme, report that instead of the spec,
+  // as the spec may be arbitrarily long and we would like to avoid
+  // copying it.
+  nsAutoCString specOrScheme;
+  nsresult rv = nsContentUtils::AnonymizeURI(aURI, specOrScheme);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  nsAutoString type;
+  type.AssignASCII(kDeprecatedOperations[static_cast<size_t>(aOperation)]);
+
+  nsAutoCString key;
+  key.AssignASCII(kDeprecatedOperations[static_cast<size_t>(aOperation)]);
+  key.AppendASCII("Warning");
+
+  nsAutoString msg;
+  rv = nsContentUtils::GetLocalizedString(nsContentUtils::eDOM_PROPERTIES,
+                                          key.get(), msg);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return;
+  }
+
+  RefPtr<DeprecationReportBody> body =
+      new DeprecationReportBody(aGlobal, type, nullptr /* date */, msg,
+                                aFileName, aLineNumber, aColumnNumber);
+
+  ReportingUtils::Report(aGlobal, nsGkAtoms::deprecation, u"default"_ns,
+                         NS_ConvertUTF8toUTF16(specOrScheme), body);
+}
+
+// This runnable is used to write a deprecation message from a worker to the
+// console running on the main-thread.
+class DeprecationWarningRunnable final
+    : public WorkerProxyToMainThreadRunnable {
+  const DeprecatedOperations mOperation;
+
+ public:
+  explicit DeprecationWarningRunnable(DeprecatedOperations aOperation)
+      : mOperation(aOperation) {}
+
+ private:
+  void RunOnMainThread(WorkerPrivate* aWorkerPrivate) override {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(aWorkerPrivate);
+
+    // Walk up to our containing page
+    WorkerPrivate* wp = aWorkerPrivate;
+    while (wp->GetParent()) {
+      wp = wp->GetParent();
+    }
+
+    nsPIDOMWindowInner* window = wp->GetWindow();
+    if (window && window->GetExtantDoc()) {
+      window->GetExtantDoc()->WarnOnceAbout(mOperation);
+    }
+  }
+
+  void RunBackOnWorkerThreadForCleanup(WorkerPrivate* aWorkerPrivate) override {
+  }
+};
+
+void MaybeShowDeprecationWarning(const GlobalObject& aGlobal,
+                                 DeprecatedOperations aOperation) {
+  if (NS_IsMainThread()) {
+    nsCOMPtr<nsPIDOMWindowInner> window =
+        do_QueryInterface(aGlobal.GetAsSupports());
+    if (window && window->GetExtantDoc()) {
+      window->GetExtantDoc()->WarnOnceAbout(aOperation);
+    }
+    return;
+  }
+
+  WorkerPrivate* workerPrivate = GetWorkerPrivateFromContext(aGlobal.Context());
+  if (!workerPrivate) {
+    return;
+  }
+
+  RefPtr<DeprecationWarningRunnable> runnable =
+      new DeprecationWarningRunnable(aOperation);
+  runnable->Dispatch(workerPrivate);
+}
+
+void MaybeReportDeprecation(const GlobalObject& aGlobal,
+                            DeprecatedOperations aOperation) {
+  nsCOMPtr<nsIURI> uri;
+
+  if (NS_IsMainThread()) {
+    nsCOMPtr<nsPIDOMWindowInner> window =
+        do_QueryInterface(aGlobal.GetAsSupports());
+    if (!window || !window->GetExtantDoc()) {
+      return;
+    }
+
+    uri = window->GetExtantDoc()->GetDocumentURI();
+  } else {
+    WorkerPrivate* workerPrivate =
+        GetWorkerPrivateFromContext(aGlobal.Context());
+    if (!workerPrivate) {
+      return;
+    }
+
+    uri = workerPrivate->GetResolvedScriptURI();
+  }
+
+  if (NS_WARN_IF(!uri)) {
+    return;
+  }
+
+  nsAutoString fileName;
+  Nullable<uint32_t> lineNumber;
+  Nullable<uint32_t> columnNumber;
+  uint32_t line = 0;
+  uint32_t column = 0;
+  if (nsJSUtils::GetCallingLocation(aGlobal.Context(), fileName, &line,
+                                    &column)) {
+    lineNumber.SetValue(line);
+    columnNumber.SetValue(column);
+  }
+
+  nsCOMPtr<nsIGlobalObject> global = do_QueryInterface(aGlobal.GetAsSupports());
+  MOZ_ASSERT(global);
+
+  ReportDeprecation(global, uri, aOperation, fileName, lineNumber,
+                    columnNumber);
+}
+
+}  // anonymous namespace
+
+void DeprecationWarning(JSContext* aCx, JSObject* aObject,
+                        DeprecatedOperations aOperation) {
+  GlobalObject global(aCx, aObject);
+  if (global.Failed()) {
+    NS_ERROR("Could not create global for DeprecationWarning");
+    return;
+  }
+
+  DeprecationWarning(global, aOperation);
+}
+
+void DeprecationWarning(const GlobalObject& aGlobal,
+                        DeprecatedOperations aOperation) {
+  MaybeShowDeprecationWarning(aGlobal, aOperation);
+  MaybeReportDeprecation(aGlobal, aOperation);
+}
+
+namespace binding_detail {
+JSObject* UnprivilegedJunkScopeOrWorkerGlobal(const fallible_t&) {
+  if (NS_IsMainThread()) {
+    return xpc::UnprivilegedJunkScope(fallible);
+  }
+
+  return GetCurrentThreadWorkerGlobal();
+}
+}  // namespace binding_detail
+
+JS::Handle<JSObject*> GetPerInterfaceObjectHandle(
+    JSContext* aCx, size_t aSlotId, CreateInterfaceObjectsMethod aCreator,
+    bool aDefineOnGlobal) {
+  /* Make sure our global is sane.  Hopefully we can remove this sometime */
+  JSObject* global = JS::CurrentGlobalOrNull(aCx);
+  if (!(JS::GetClass(global)->flags & JSCLASS_DOM_GLOBAL)) {
+    return nullptr;
+  }
+
+  /* Check to see whether the interface objects are already installed */
+  ProtoAndIfaceCache& protoAndIfaceCache = *GetProtoAndIfaceCache(global);
+  if (!protoAndIfaceCache.HasEntryInSlot(aSlotId)) {
+    JS::Rooted<JSObject*> rootedGlobal(aCx, global);
+    aCreator(aCx, rootedGlobal, protoAndIfaceCache, aDefineOnGlobal);
+  }
+
+  /*
+   * The object might _still_ be null, but that's OK.
+   *
+   * Calling fromMarkedLocation() is safe because protoAndIfaceCache is
+   * traced by TraceProtoAndIfaceCache() and its contents are never
+   * changed after they have been set.
+   *
+   * Calling address() avoids the read barrier that does gray unmarking, but
+   * it's not possible for the object to be gray here.
+   */
+
+  const JS::Heap<JSObject*>& entrySlot =
+      protoAndIfaceCache.EntrySlotMustExist(aSlotId);
+  JS::AssertObjectIsNotGray(entrySlot);
+  return JS::Handle<JSObject*>::fromMarkedLocation(entrySlot.address());
+}
+
+namespace binding_detail {
+bool IsGetterEnabled(JSContext* aCx, JS::Handle<JSObject*> aObj,
+                     JSJitGetterOp aGetter,
+                     const Prefable<const JSPropertySpec>* aAttributes) {
+  MOZ_ASSERT(aAttributes);
+  MOZ_ASSERT(aAttributes->specs);
+  do {
+    if (aAttributes->isEnabled(aCx, aObj)) {
+      const JSPropertySpec* specs = aAttributes->specs;
+      do {
+        if (!specs->isAccessor() || specs->isSelfHosted()) {
+          // It won't have a JSJitGetterOp.
+          continue;
+        }
+        const JSJitInfo* info = specs->u.accessors.getter.native.info;
+        if (!info) {
+          continue;
+        }
+        MOZ_ASSERT(info->type() == JSJitInfo::OpType::Getter);
+        if (info->getter == aGetter) {
+          return true;
+        }
+      } while ((++specs)->name);
+    }
+  } while ((++aAttributes)->specs);
+
+  // Didn't find it.
+  return false;
+}
+
+already_AddRefed<Promise> CreateRejectedPromiseFromThrownException(
+    JSContext* aCx, ErrorResult& aError) {
+  if (!JS_IsExceptionPending(aCx)) {
+    // If there is no pending exception here but we're ending up in this code,
+    // that means the callee threw an uncatchable exception. Just propagate that
+    // out as-is. Promise::RejectWithExceptionFromContext also checks this, but
+    // we want to bail out here before trying to get the globals.
+    aError.ThrowUncatchableException();
+    return nullptr;
+  }
+
+  GlobalObject promiseGlobal(aCx, GetEntryGlobal()->GetGlobalJSObject());
+  if (promiseGlobal.Failed()) {
+    aError.StealExceptionFromJSContext(aCx);
+    return nullptr;
+  }
+
+  nsCOMPtr<nsIGlobalObject> global =
+      do_QueryInterface(promiseGlobal.GetAsSupports());
+  if (!global) {
+    aError.Throw(NS_ERROR_UNEXPECTED);
+    return nullptr;
+  }
+
+  return Promise::RejectWithExceptionFromContext(global, aCx, aError);
+}
+
+}  // namespace binding_detail
+
+}  // namespace dom
+}  // namespace mozilla