Bug 1224061: Make Event::InitEvent infallible. r=smaug

2015-11-13 08:09:42 +08:00 · 2015-11-13 08:09:42 +08:00 · bdbb2ec50a
--- a/dom/base/DOMRequest.cpp
+++ b/dom/base/DOMRequest.cpp
@ -193,11 +193,7 @@ DOMRequest::FireEvent(const nsAString& aType, bool aBubble, bool aCancelable)
  }

  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-  nsresult rv = event->InitEvent(aType, aBubble, aCancelable);
-  if (NS_FAILED(rv)) {
-    return;
-  }
-
+  event->InitEvent(aType, aBubble, aCancelable);
  event->SetTrusted(true);

  bool dummy;
--- a/dom/base/EventSource.cpp
+++ b/dom/base/EventSource.cpp
@ -757,12 +757,7 @@ EventSource::AnnounceConnection()
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

  // it doesn't bubble, and it isn't cancelable
-  rv = event->InitEvent(NS_LITERAL_STRING("open"), false, false);
-  if (NS_FAILED(rv)) {
-    NS_WARNING("Failed to init the open event!!!");
-    return;
-  }
-
+  event->InitEvent(NS_LITERAL_STRING("open"), false, false);
  event->SetTrusted(true);

  rv = DispatchDOMEvent(nullptr, event, nullptr, nullptr);
@ -813,12 +808,7 @@ EventSource::ReestablishConnection()
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

  // it doesn't bubble, and it isn't cancelable
-  rv = event->InitEvent(NS_LITERAL_STRING("error"), false, false);
-  if (NS_FAILED(rv)) {
-    NS_WARNING("Failed to init the error event!!!");
-    return;
-  }
-
+  event->InitEvent(NS_LITERAL_STRING("error"), false, false);
  event->SetTrusted(true);

  rv = DispatchDOMEvent(nullptr, event, nullptr, nullptr);
@ -964,12 +954,7 @@ EventSource::FailConnection()
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

  // it doesn't bubble, and it isn't cancelable
-  rv = event->InitEvent(NS_LITERAL_STRING("error"), false, false);
-  if (NS_FAILED(rv)) {
-    NS_WARNING("Failed to init the error event!!!");
-    return;
-  }
-
+  event->InitEvent(NS_LITERAL_STRING("error"), false, false);
  event->SetTrusted(true);

  rv = DispatchDOMEvent(nullptr, event, nullptr, nullptr);
--- a/dom/base/WebSocket.cpp
+++ b/dom/base/WebSocket.cpp
@ -1807,9 +1807,7 @@ WebSocket::CreateAndDispatchSimpleEvent(const nsAString& aName)
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

  // it doesn't bubble, and it isn't cancelable
-  rv = event->InitEvent(aName, false, false);
-  NS_ENSURE_SUCCESS(rv, rv);
-
+  event->InitEvent(aName, false, false);
  event->SetTrusted(true);

  return DispatchDOMEvent(nullptr, event, nullptr, nullptr);
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@ -3756,9 +3756,7 @@ nsresult GetEventAndTarget(nsIDocument* aDoc, nsISupports* aTarget,
    domDoc->CreateEvent(NS_LITERAL_STRING("Events"), getter_AddRefs(event));
  NS_ENSURE_SUCCESS(rv, rv);

-  rv = event->InitEvent(aEventName, aCanBubble, aCancelable);
-  NS_ENSURE_SUCCESS(rv, rv);
-
+  event->InitEvent(aEventName, aCanBubble, aCancelable);
  event->SetTrusted(aTrusted);

  rv = event->SetTarget(target);
--- a/dom/base/nsDOMDataChannel.cpp
+++ b/dom/base/nsDOMDataChannel.cpp
@ -455,9 +455,7 @@ nsDOMDataChannel::OnSimpleEvent(nsISupports* aContext, const nsAString& aName)

  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

-  rv = event->InitEvent(aName, false, false);
-  NS_ENSURE_SUCCESS(rv,rv);
-
+  event->InitEvent(aName, false, false);
  event->SetTrusted(true);

  return DispatchDOMEvent(nullptr, event, nullptr, nullptr);
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@ -9122,10 +9122,7 @@ DispatchCustomEventWithFlush(nsINode* aTarget, const nsAString& aEventType,
                             bool aBubbles, bool aOnlyChromeDispatch)
 {
  RefPtr<Event> event = NS_NewDOMEvent(aTarget, nullptr, nullptr);
-  nsresult rv = event->InitEvent(aEventType, aBubbles, false);
-  if (NS_FAILED(rv)) {
-    return;
-  }
+  event->InitEvent(aEventType, aBubbles, false);
  event->SetTrusted(true);
  if (aOnlyChromeDispatch) {
    event->GetInternalNSEvent()->mFlags.mOnlyChromeDispatch = true;
--- a/dom/base/nsGlobalWindow.cpp
+++ b/dom/base/nsGlobalWindow.cpp
@ -11028,13 +11028,11 @@ nsGlobalWindow::Observe(nsISupports* aSubject, const char* aTopic,
    }

    RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-    nsresult rv = event->InitEvent(
+    event->InitEvent(
      !nsCRT::strcmp(aTopic, NS_NETWORK_ACTIVITY_BLIP_UPLOAD_TOPIC)
        ? NETWORK_UPLOAD_EVENT_NAME
        : NETWORK_DOWNLOAD_EVENT_NAME,
      false, false);
-    NS_ENSURE_SUCCESS(rv, rv);
-
    event->SetTrusted(true);

    bool dummy;
@ -11064,9 +11062,7 @@ nsGlobalWindow::Observe(nsISupports* aSubject, const char* aTopic,
    }

    RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-    nsresult rv = event->InitEvent(NS_LITERAL_STRING("languagechange"), false, false);
-    NS_ENSURE_SUCCESS(rv, rv);
-
+    event->InitEvent(NS_LITERAL_STRING("languagechange"), false, false);
    event->SetTrusted(true);

    bool dummy;
--- a/dom/base/nsPerformance.cpp
+++ b/dom/base/nsPerformance.cpp
@ -483,11 +483,7 @@ nsPerformance::DispatchBufferFullEvent()
 {
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
  // it bubbles, and it isn't cancelable
-  nsresult rv = event->InitEvent(NS_LITERAL_STRING("resourcetimingbufferfull"),
-                                 true, false);
-  if (NS_FAILED(rv)) {
-    return;
-  }
+  event->InitEvent(NS_LITERAL_STRING("resourcetimingbufferfull"), true, false);
  event->SetTrusted(true);
  DispatchDOMEvent(nullptr, event, nullptr, nullptr);
 }
--- a/dom/bindings/Codegen.py
+++ b/dom/bindings/Codegen.py
@ -15977,7 +15977,7 @@ class CGEventMethod(CGNativeMember):
            self.args.insert(0, Argument("JSContext*", "aCx"))
        if not self.isInit:
            self.args.insert(0, Argument("const GlobalObject&", "aGlobal"))
-        self.args.append(Argument('ErrorResult&', 'aRv'))
+            self.args.append(Argument('ErrorResult&', 'aRv'))
        return constructorForNativeCaller + CGNativeMember.declare(self, cgClass)

    def defineInit(self, cgClass):
@ -15999,11 +15999,7 @@ class CGEventMethod(CGNativeMember):

        self.body = fill(
            """
-            nsresult rv = InitEvent(${typeArg}, ${bubblesArg}, ${cancelableArg});
-            if (NS_FAILED(rv)) {
-              aRv.Throw(rv);
-              return;
-            }
+            InitEvent(${typeArg}, ${bubblesArg}, ${cancelableArg});
            ${members}
            """,
            typeArg=self.args[0].name,
@ -16011,8 +16007,6 @@ class CGEventMethod(CGNativeMember):
            cancelableArg=self.args[2].name,
            members=members)

-        self.args.append(Argument('ErrorResult&', 'aRv'))
-
        return CGNativeMember.define(self, cgClass)

    def define(self, cgClass):
--- a/dom/events/AnimationEvent.cpp
+++ b/dom/events/AnimationEvent.cpp
@ -44,7 +44,7 @@ AnimationEvent::Constructor(const GlobalObject& aGlobal,
  RefPtr<AnimationEvent> e = new AnimationEvent(t, nullptr, nullptr);
  bool trusted = e->Init(t);

-  aRv = e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
+  e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);

  InternalAnimationEvent* internalEvent = e->mEvent->AsAnimationEvent();
  internalEvent->animationName = aParam.mAnimationName;
--- a/dom/events/AsyncEventDispatcher.cpp
+++ b/dom/events/AsyncEventDispatcher.cpp
@ -40,8 +40,7 @@ AsyncEventDispatcher::Run()
  RefPtr<Event> event = mEvent ? mEvent->InternalDOMEvent() : nullptr;
  if (!event) {
    event = NS_NewDOMEvent(mTarget, nullptr, nullptr);
-    nsresult rv = event->InitEvent(mEventType, mBubbles, false);
-    NS_ENSURE_SUCCESS(rv, rv);
+    event->InitEvent(mEventType, mBubbles, false);
    event->SetTrusted(true);
  }
  if (mOnlyChromeDispatch) {
--- a/dom/events/ClipboardEvent.cpp
+++ b/dom/events/ClipboardEvent.cpp
@ -43,7 +43,7 @@ ClipboardEvent::InitClipboardEvent(const nsAString& aType,
  // Null clipboardData is OK

  ErrorResult rv;
-  InitClipboardEvent(aType, aCanBubble, aCancelable, clipboardData, rv);
+  InitClipboardEvent(aType, aCanBubble, aCancelable, clipboardData);

  return rv.StealNSResult();
 }
@ -51,14 +51,9 @@ ClipboardEvent::InitClipboardEvent(const nsAString& aType,
 void
 ClipboardEvent::InitClipboardEvent(const nsAString& aType, bool aCanBubble,
                                   bool aCancelable,
-                                   DataTransfer* aClipboardData,
-                                   ErrorResult& aError)
+                                   DataTransfer* aClipboardData)
 {
-  aError = Event::InitEvent(aType, aCanBubble, aCancelable);
-  if (aError.Failed()) {
-    return;
-  }
-
+  Event::InitEvent(aType, aCanBubble, aCancelable);
  mEvent->AsClipboardEvent()->clipboardData = aClipboardData;
 }

@ -86,7 +81,7 @@ ClipboardEvent::Constructor(const GlobalObject& aGlobal,
  }

  e->InitClipboardEvent(aType, aParam.mBubbles, aParam.mCancelable,
-                        clipboardData, aRv);
+                        clipboardData);
  e->SetTrusted(trusted);
  return e.forget();
 }
--- a/dom/events/ClipboardEvent.h
+++ b/dom/events/ClipboardEvent.h
@ -46,8 +46,7 @@ public:

  void InitClipboardEvent(const nsAString& aType, bool aCanBubble,
                          bool aCancelable,
-                          DataTransfer* aClipboardData,
-                          ErrorResult& aError);
+                          DataTransfer* aClipboardData);

 protected:
  ~ClipboardEvent() {}
--- a/dom/events/CommandEvent.cpp
+++ b/dom/events/CommandEvent.cpp
@ -51,8 +51,7 @@ CommandEvent::InitCommandEvent(const nsAString& aTypeArg,
                               bool aCancelableArg,
                               const nsAString& aCommand)
 {
-  nsresult rv = Event::InitEvent(aTypeArg, aCanBubbleArg, aCancelableArg);
-  NS_ENSURE_SUCCESS(rv, rv);
+  Event::InitEvent(aTypeArg, aCanBubbleArg, aCancelableArg);

  mEvent->AsCommandEvent()->command = do_GetAtom(aCommand);
  return NS_OK;
--- a/dom/events/CustomEvent.cpp
+++ b/dom/events/CustomEvent.cpp
@ -66,8 +66,7 @@ CustomEvent::InitCustomEvent(const nsAString& aType,
                             bool aCancelable,
                             nsIVariant* aDetail)
 {
-  nsresult rv = Event::InitEvent(aType, aCanBubble, aCancelable);
-  NS_ENSURE_SUCCESS(rv, rv);
+  Event::InitEvent(aType, aCanBubble, aCancelable);
  mDetail = aDetail;
  return NS_OK;
 }
@ -89,7 +88,7 @@ CustomEvent::InitCustomEvent(JSContext* aCx,
    aRv.Throw(NS_ERROR_FAILURE);
    return;
  }
-  aRv = InitCustomEvent(aType, aCanBubble, aCancelable, detail);
+  InitCustomEvent(aType, aCanBubble, aCancelable, detail);
 }

 NS_IMETHODIMP
--- a/dom/events/DOMEventTargetHelper.cpp
+++ b/dom/events/DOMEventTargetHelper.cpp
@ -263,8 +263,7 @@ nsresult
 DOMEventTargetHelper::DispatchTrustedEvent(const nsAString& aEventName)
 {
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-  nsresult rv = event->InitEvent(aEventName, false, false);
-  NS_ENSURE_SUCCESS(rv, rv);
+  event->InitEvent(aEventName, false, false);

  return DispatchTrustedEvent(event);
 }
--- a/dom/events/DeviceMotionEvent.cpp
+++ b/dom/events/DeviceMotionEvent.cpp
@ -33,13 +33,9 @@ DeviceMotionEvent::InitDeviceMotionEvent(
                     const DeviceAccelerationInit& aAcceleration,
                     const DeviceAccelerationInit& aAccelIncludingGravity,
                     const DeviceRotationRateInit& aRotationRate,
-                     Nullable<double> aInterval,
-                     ErrorResult& aRv)
+                     Nullable<double> aInterval)
 {
-  aRv = Event::InitEvent(aType, aCanBubble, aCancelable);
-  if (aRv.Failed()) {
-    return;
-  }
+  Event::InitEvent(aType, aCanBubble, aCancelable);

  mAcceleration = new DeviceAcceleration(this, aAcceleration.mX,
                                         aAcceleration.mY,
@ -64,10 +60,7 @@ DeviceMotionEvent::Constructor(const GlobalObject& aGlobal,
 {
  nsCOMPtr<EventTarget> t = do_QueryInterface(aGlobal.GetAsSupports());
  RefPtr<DeviceMotionEvent> e = new DeviceMotionEvent(t, nullptr, nullptr);
-  aRv = e->InitEvent(aType, aEventInitDict.mBubbles, aEventInitDict.mCancelable);
-  if (aRv.Failed()) {
-    return nullptr;
-  }
+  e->InitEvent(aType, aEventInitDict.mBubbles, aEventInitDict.mCancelable);
  bool trusted = e->Init(t);

  e->mAcceleration = new DeviceAcceleration(e,
--- a/dom/events/DeviceMotionEvent.h
+++ b/dom/events/DeviceMotionEvent.h
@ -128,8 +128,7 @@ public:
         const DeviceAccelerationInit& aAcceleration,
         const DeviceAccelerationInit& aAccelerationIncludingGravity,
         const DeviceRotationRateInit& aRotationRate,
-         Nullable<double> aInterval,
-         ErrorResult& aRv);
+         Nullable<double> aInterval);

  static already_AddRefed<DeviceMotionEvent>
  Constructor(const GlobalObject& aGlobal,
--- a/dom/events/Event.cpp
+++ b/dom/events/Event.cpp
@ -414,7 +414,7 @@ Event::Constructor(const GlobalObject& aGlobal,
  nsCOMPtr<mozilla::dom::EventTarget> t = do_QueryInterface(aGlobal.GetAsSupports());
  RefPtr<Event> e = new Event(t, nullptr, nullptr);
  bool trusted = e->Init(t);
-  aRv = e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
+  e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
  e->SetTrusted(trusted);
  return e.forget();
 }
@ -572,13 +572,13 @@ Event::SetEventType(const nsAString& aEventTypeArg)
  }
 }

-NS_IMETHODIMP
+void
 Event::InitEvent(const nsAString& aEventTypeArg,
                 bool aCanBubbleArg,
                 bool aCancelableArg)
 {
  // Make sure this event isn't already being dispatched.
-  NS_ENSURE_TRUE(!mEvent->mFlags.mIsBeingDispatched, NS_OK);
+  NS_ENSURE_TRUE_VOID(!mEvent->mFlags.mIsBeingDispatched);

  if (IsTrusted()) {
    // Ensure the caller is permitted to dispatch trusted DOM events.
@ -600,7 +600,6 @@ Event::InitEvent(const nsAString& aEventTypeArg,
  // re-dispatching it.
  mEvent->target = nullptr;
  mEvent->originalTarget = nullptr;
-  return NS_OK;
 }

 NS_IMETHODIMP
@ -1190,8 +1189,7 @@ Event::Deserialize(const IPC::Message* aMsg, void** aIter)
  bool trusted = false;
  NS_ENSURE_TRUE(IPC::ReadParam(aMsg, aIter, &trusted), false);

-  nsresult rv = InitEvent(type, bubbles, cancelable);
-  NS_ENSURE_SUCCESS(rv, false);
+  InitEvent(type, bubbles, cancelable);
  SetTrusted(trusted);

  return true;
--- a/dom/events/Event.h
+++ b/dom/events/Event.h
@ -206,12 +206,6 @@ public:

  double TimeStamp() const;

-  void InitEvent(const nsAString& aType, bool aBubbles, bool aCancelable,
-                 ErrorResult& aRv)
-  {
-    aRv = InitEvent(aType, aBubbles, aCancelable);
-  }
-
  EventTarget* GetOriginalTarget() const;
  EventTarget* GetExplicitOriginalTarget() const;
  EventTarget* GetComposedTarget() const;
@ -312,7 +306,7 @@ private:
  NS_IMETHOD StopPropagation(void) override { return _to StopPropagation(); } \
  NS_IMETHOD StopCrossProcessForwarding(void) override { return _to StopCrossProcessForwarding(); } \
  NS_IMETHOD PreventDefault(void) override { return _to PreventDefault(); } \
-  NS_IMETHOD InitEvent(const nsAString& eventTypeArg, bool canBubbleArg, bool cancelableArg) override { return _to InitEvent(eventTypeArg, canBubbleArg, cancelableArg); } \
+  void InitEvent(const nsAString& eventTypeArg, bool canBubbleArg, bool cancelableArg) override { _to InitEvent(eventTypeArg, canBubbleArg, cancelableArg); } \
  NS_IMETHOD GetDefaultPrevented(bool* aDefaultPrevented) override { return _to GetDefaultPrevented(aDefaultPrevented); } \
  NS_IMETHOD StopImmediatePropagation(void) override { return _to StopImmediatePropagation(); } \
  NS_IMETHOD GetOriginalTarget(nsIDOMEventTarget** aOriginalTarget) override { return _to GetOriginalTarget(aOriginalTarget); } \
--- a/dom/events/MessageEvent.cpp
+++ b/dom/events/MessageEvent.cpp
@ -131,11 +131,7 @@ MessageEvent::Constructor(EventTarget* aEventTarget,
 {
  RefPtr<MessageEvent> event = new MessageEvent(aEventTarget, nullptr, nullptr);

-  aRv = event->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
-  if (aRv.Failed()) {
-    return nullptr;
-  }
-
+  event->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
  bool trusted = event->Init(aEventTarget);
  event->SetTrusted(trusted);

@ -182,9 +178,7 @@ MessageEvent::InitMessageEvent(const nsAString& aType,
                               const nsAString& aLastEventId,
                               nsIDOMWindow* aSource)
 {
-  nsresult rv = Event::InitEvent(aType, aCanBubble, aCancelable);
-  NS_ENSURE_SUCCESS(rv, rv);
-
+  Event::InitEvent(aType, aCanBubble, aCancelable);
  mData = aData;
  mozilla::HoldJSObjects(this);
  mOrigin = aOrigin;
@ -201,14 +195,9 @@ MessageEvent::InitMessageEvent(JSContext* aCx, const nsAString& aType,
                               const nsAString& aOrigin,
                               const nsAString& aLastEventId,
                               const Nullable<WindowProxyOrMessagePort>& aSource,
-                               const Nullable<Sequence<OwningNonNull<MessagePort>>>& aPorts,
-                               ErrorResult& aRv)
+                               const Nullable<Sequence<OwningNonNull<MessagePort>>>& aPorts)
 {
-  aRv = Event::InitEvent(aType, aCanBubble, aCancelable);
-  if (NS_WARN_IF(aRv.Failed())) {
-    return;
-  }
-
+  Event::InitEvent(aType, aCanBubble, aCancelable);
  mData = aData;
  mozilla::HoldJSObjects(this);
  mOrigin = aOrigin;
--- a/dom/events/MessageEvent.h
+++ b/dom/events/MessageEvent.h
@ -83,8 +83,7 @@ public:
                        bool aCancelable, JS::Handle<JS::Value> aData,
                        const nsAString& aOrigin, const nsAString& aLastEventId,
                        const Nullable<WindowProxyOrMessagePort>& aSource,
-                        const Nullable<Sequence<OwningNonNull<MessagePort>>>& aPorts,
-                        ErrorResult& aRv);
+                        const Nullable<Sequence<OwningNonNull<MessagePort>>>& aPorts);

 protected:
  ~MessageEvent();
--- a/dom/events/MutationEvent.cpp
+++ b/dom/events/MutationEvent.cpp
@ -96,8 +96,7 @@ MutationEvent::InitMutationEvent(const nsAString& aTypeArg,
                                 const nsAString& aAttrNameArg,
                                 uint16_t aAttrChangeArg)
 {
-  nsresult rv = Event::InitEvent(aTypeArg, aCanBubbleArg, aCancelableArg);
-  NS_ENSURE_SUCCESS(rv, rv);
+  Event::InitEvent(aTypeArg, aCanBubbleArg, aCancelableArg);

  InternalMutationEvent* mutation = mEvent->AsMutationEvent();
  mutation->mRelatedNode = aRelatedNodeArg;
--- a/dom/events/SpeechRecognitionError.cpp
+++ b/dom/events/SpeechRecognitionError.cpp
@ -29,7 +29,7 @@ SpeechRecognitionError::Constructor(const GlobalObject& aGlobal,
  nsCOMPtr<mozilla::dom::EventTarget> t = do_QueryInterface(aGlobal.GetAsSupports());
  RefPtr<SpeechRecognitionError> e = new SpeechRecognitionError(t, nullptr, nullptr);
  bool trusted = e->Init(t);
-  e->InitSpeechRecognitionError(aType, aParam.mBubbles, aParam.mCancelable, aParam.mError, aParam.mMessage, aRv);
+  e->InitSpeechRecognitionError(aType, aParam.mBubbles, aParam.mCancelable, aParam.mError, aParam.mMessage);
  e->SetTrusted(trusted);
  return e.forget();
 }
@ -39,15 +39,11 @@ SpeechRecognitionError::InitSpeechRecognitionError(const nsAString& aType,
                                                   bool aCanBubble,
                                                   bool aCancelable,
                                                   SpeechRecognitionErrorCode aError,
-                                                   const nsAString& aMessage,
-                                                   ErrorResult& aRv)
+                                                   const nsAString& aMessage)
 {
-  aRv = Event::InitEvent(aType, aCanBubble, aCancelable);
-  NS_ENSURE_TRUE_VOID(!aRv.Failed());
-
+  Event::InitEvent(aType, aCanBubble, aCancelable);
  mError = aError;
  mMessage = aMessage;
-  return;
 }

 } // namespace dom
--- a/dom/events/SpeechRecognitionError.h
+++ b/dom/events/SpeechRecognitionError.h
@ -49,8 +49,7 @@ public:
                             bool aCanBubble,
                             bool aCancelable,
                             SpeechRecognitionErrorCode aError,
-                             const nsAString& aMessage,
-                             ErrorResult& aRv);
+                             const nsAString& aMessage);

 protected:
  SpeechRecognitionErrorCode mError;
--- a/dom/events/StorageEvent.cpp
+++ b/dom/events/StorageEvent.cpp
@ -85,14 +85,9 @@ StorageEvent::InitStorageEvent(const nsAString& aType, bool aCanBubble,
                               const nsAString& aOldValue,
                               const nsAString& aNewValue,
                               const nsAString& aURL,
-                               DOMStorage* aStorageArea,
-                               ErrorResult& aRv)
+                               DOMStorage* aStorageArea)
 {
-  aRv = InitEvent(aType, aCanBubble, aCancelable);
-  if (aRv.Failed()) {
-    return;
-  }
-
+  InitEvent(aType, aCanBubble, aCancelable);
  mKey = aKey;
  mOldValue = aOldValue;
  mNewValue = aNewValue;
--- a/dom/events/StorageEvent.h
+++ b/dom/events/StorageEvent.h
@ -57,8 +57,7 @@ public:
                        const nsAString& aOldValue,
                        const nsAString& aNewValue,
                        const nsAString& aURL,
-                        DOMStorage* aStorageArea,
-                        ErrorResult& aRv);
+                        DOMStorage* aStorageArea);

  void GetKey(nsString& aRetVal) const
  {
--- a/dom/events/TouchEvent.cpp
+++ b/dom/events/TouchEvent.cpp
@ -102,14 +102,9 @@ TouchEvent::InitTouchEvent(const nsAString& aType,
                           bool aMetaKey,
                           TouchList* aTouches,
                           TouchList* aTargetTouches,
-                           TouchList* aChangedTouches,
-                           ErrorResult& aRv)
+                           TouchList* aChangedTouches)
 {
-  aRv = UIEvent::InitUIEvent(aType, aCanBubble, aCancelable, aView, aDetail);
-  if (aRv.Failed()) {
-    return;
-  }
-
+  UIEvent::InitUIEvent(aType, aCanBubble, aCancelable, aView, aDetail);
  mEvent->AsInputEvent()->InitBasicModifiers(aCtrlKey, aAltKey,
                                             aShiftKey, aMetaKey);
  mTouches = aTouches;
--- a/dom/events/TouchEvent.h
+++ b/dom/events/TouchEvent.h
@ -115,8 +115,7 @@ public:
                      bool aMetaKey,
                      TouchList* aTouches,
                      TouchList* aTargetTouches,
-                      TouchList* aChangedTouches,
-                      ErrorResult& aRv);
+                      TouchList* aChangedTouches);

  static bool PrefEnabled(JSContext* aCx = nullptr,
                          JSObject* aGlobal = nullptr);
--- a/dom/events/TransitionEvent.cpp
+++ b/dom/events/TransitionEvent.cpp
@ -44,7 +44,7 @@ TransitionEvent::Constructor(const GlobalObject& aGlobal,
  RefPtr<TransitionEvent> e = new TransitionEvent(t, nullptr, nullptr);
  bool trusted = e->Init(t);

-  aRv = e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
+  e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);

  InternalTransitionEvent* internalEvent = e->mEvent->AsTransitionEvent();
  internalEvent->propertyName = aParam.mPropertyName;
--- a/dom/events/UIEvent.cpp
+++ b/dom/events/UIEvent.cpp
@ -161,9 +161,7 @@ UIEvent::InitUIEvent(const nsAString& typeArg,
    nsCOMPtr<nsPIDOMWindow> view = do_QueryInterface(viewArg);
    NS_ENSURE_TRUE(view, NS_ERROR_INVALID_ARG);
  }
-  nsresult rv = Event::InitEvent(typeArg, canBubbleArg, cancelableArg);
-  NS_ENSURE_SUCCESS(rv, rv);
-  
+  Event::InitEvent(typeArg, canBubbleArg, cancelableArg);
  mDetail = detailArg;
  mView = viewArg;

--- a/dom/indexedDB/IDBEvents.cpp
+++ b/dom/indexedDB/IDBEvents.cpp
@ -35,10 +35,9 @@ CreateGenericEvent(EventTarget* aOwner,
 {
  RefPtr<Event> event = new Event(aOwner, nullptr, nullptr);

-  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(
-    event->InitEvent(aType,
-                     aBubbles == eDoesBubble ? true : false,
-                     aCancelable == eCancelable ? true : false)));
+  event->InitEvent(aType,
+                   aBubbles == eDoesBubble ? true : false,
+                   aCancelable == eCancelable ? true : false);

  event->SetTrusted(true);

@ -58,7 +57,7 @@ IDBVersionChangeEvent::CreateInternal(EventTarget* aOwner,
    event->mNewVersion.SetValue(aNewVersion.Value());
  }

-  MOZ_ALWAYS_TRUE(NS_SUCCEEDED(event->InitEvent(aType, false, false)));
+  event->InitEvent(aType, false, false);

  event->SetTrusted(true);

--- a/dom/interfaces/events/nsIDOMAnimationEvent.idl
+++ b/dom/interfaces/events/nsIDOMAnimationEvent.idl
@ -11,7 +11,7 @@
 * http://dev.w3.org/csswg/css3-animations/#animation-events-
 */

-[builtinclass, uuid(b1bea1bc-689b-4e07-8cbc-ef342725f9a6)]
+[builtinclass, uuid(772c7069-3f7d-42cf-97ab-b32f1c0b83da)]
 interface nsIDOMAnimationEvent : nsIDOMEvent {
  readonly attribute DOMString          animationName;
  readonly attribute float              elapsedTime;
--- a/dom/interfaces/events/nsIDOMBeforeUnloadEvent.idl
+++ b/dom/interfaces/events/nsIDOMBeforeUnloadEvent.idl
@ -15,7 +15,7 @@
 *
 */

-[builtinclass, uuid(ee7b8943-440e-4cc3-b25e-c17c8a821d8b)]
+[builtinclass, uuid(96abf41b-32a8-4ff6-a0d6-4ade4ddebf89)]
 interface nsIDOMBeforeUnloadEvent : nsIDOMEvent
 {
  /**
--- a/dom/interfaces/events/nsIDOMClipboardEvent.idl
+++ b/dom/interfaces/events/nsIDOMClipboardEvent.idl
@ -8,7 +8,7 @@

 interface nsIDOMDataTransfer;

-[builtinclass, uuid(8D92944A-F2E5-41F4-9CF3-D85043B90CAC)]
+[builtinclass, uuid(4ef84980-52c2-425c-b41a-2ee75ec5d497)]
 interface nsIDOMClipboardEvent : nsIDOMEvent
 {
  readonly attribute nsIDOMDataTransfer clipboardData;
--- a/dom/interfaces/events/nsIDOMCommandEvent.idl
+++ b/dom/interfaces/events/nsIDOMCommandEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMEvent.idl"

-[builtinclass, uuid(3fdc07cb-3b2e-4c6e-a054-008a4f302202)]
+[builtinclass, uuid(7efbe68a-811a-4159-801c-226948cfd08f)]
 interface nsIDOMCommandEvent : nsIDOMEvent
 {
  readonly attribute DOMString command;
--- a/dom/interfaces/events/nsIDOMCompositionEvent.idl
+++ b/dom/interfaces/events/nsIDOMCompositionEvent.idl
@ -6,7 +6,7 @@

 #include "nsIDOMUIEvent.idl"

-[builtinclass, uuid(ef545b90-a5f4-471c-b4f8-03b5e0f6fda2)]
+[builtinclass, uuid(5adfd99b-d3c7-4c6d-92d1-527264a71b50)]
 interface nsIDOMCompositionEvent : nsIDOMUIEvent
 {
  readonly attribute DOMString data;
--- a/dom/interfaces/events/nsIDOMCustomEvent.idl
+++ b/dom/interfaces/events/nsIDOMCustomEvent.idl
@ -6,7 +6,7 @@
 #include "nsIDOMEvent.idl"
 interface nsIVariant;

-[builtinclass, uuid(b56ae6ca-c822-489e-be71-2a9f3c56082e)]
+[builtinclass, uuid(55fa3a13-4812-45a7-98b7-3be6cec2df43)]
 interface nsIDOMCustomEvent : nsIDOMEvent
 {

--- a/dom/interfaces/events/nsIDOMDataContainerEvent.idl
+++ b/dom/interfaces/events/nsIDOMDataContainerEvent.idl
@ -6,7 +6,7 @@
 #include "nsIDOMEvent.idl"
 #include "nsIVariant.idl"

-[builtinclass, uuid(dc6b39da-87ff-4b6f-b065-b52602602e06)]
+[builtinclass, uuid(31ceb43e-5f49-43bf-9a18-3b60a535c814)]
 interface nsIDOMDataContainerEvent : nsIDOMEvent
 {
  /**
--- a/dom/interfaces/events/nsIDOMDragEvent.idl
+++ b/dom/interfaces/events/nsIDOMDragEvent.idl
@ -8,7 +8,7 @@

 interface nsIDOMDataTransfer;

-[builtinclass, uuid(4d0fe952-7ca7-4730-a163-4454e39ed187)]
+[builtinclass, uuid(12aabbe9-7c70-4bf9-b133-a8d6a120679e)]
 interface nsIDOMDragEvent : nsIDOMMouseEvent
 {
  readonly attribute nsIDOMDataTransfer dataTransfer;
--- a/dom/interfaces/events/nsIDOMEvent.idl
+++ b/dom/interfaces/events/nsIDOMEvent.idl
@ -40,7 +40,7 @@ class EventTarget;
 * http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html
 */

-[builtinclass, uuid(63857daf-c084-4ea6-a8b9-6812e3176991)]
+[builtinclass, uuid(f58daacf-4d1a-4002-8fd7-06b614dfbcf6)]
 interface nsIDOMEvent : nsISupports
 {
  // PhaseType
@ -161,6 +161,7 @@ interface nsIDOMEvent : nsISupports
   * @param   cancelableArg Specifies whether or not the event's default 
   *                        action can be prevented.
   */
+  [notxpcom]
  void                      initEvent(in DOMString eventTypeArg,
                                      in boolean canBubbleArg,
                                      in boolean cancelableArg);
--- a/dom/interfaces/events/nsIDOMFocusEvent.idl
+++ b/dom/interfaces/events/nsIDOMFocusEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMUIEvent.idl"

-[builtinclass, uuid(4faecbd6-1bcd-42d8-bc66-ec6b95050063)]
+[builtinclass, uuid(f2606aee-1801-4e4c-9700-af99e435c02c)]
 interface nsIDOMFocusEvent : nsIDOMUIEvent
 {
  readonly attribute nsIDOMEventTarget  relatedTarget;
--- a/dom/interfaces/events/nsIDOMKeyEvent.idl
+++ b/dom/interfaces/events/nsIDOMKeyEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMUIEvent.idl"

-[builtinclass, uuid(d2b3e35f-8627-4732-a92d-cda54c8f8054)]
+[builtinclass, uuid(f4082a63-73c0-49ad-86e0-c406a54573f7)]
 interface nsIDOMKeyEvent : nsIDOMUIEvent
 {
  const unsigned long DOM_VK_CANCEL         = 0x03;
--- a/dom/interfaces/events/nsIDOMMessageEvent.idl
+++ b/dom/interfaces/events/nsIDOMMessageEvent.idl
@ -12,7 +12,7 @@
 * For more information on this interface, please see
 * http://www.whatwg.org/specs/web-apps/current-work/#messageevent
 */
-[builtinclass, uuid(bb869a03-5fc0-4a1b-838a-342e5025fc05)]
+[builtinclass, uuid(4408a2f5-614f-40a3-8786-e16bd3f74e32)]
 interface nsIDOMMessageEvent : nsIDOMEvent
 {
  /**
--- a/dom/interfaces/events/nsIDOMMouseEvent.idl
+++ b/dom/interfaces/events/nsIDOMMouseEvent.idl
@ -13,7 +13,7 @@
 * http://www.w3.org/TR/DOM-Level-2-Events/
 */

-[builtinclass, uuid(df068636-9a5b-11e3-b71f-2c27d728e7f9)]
+[builtinclass, uuid(dbebc4be-75c9-47ca-aee8-0a8b4ae14a87)]
 interface nsIDOMMouseEvent : nsIDOMUIEvent
 {
  readonly attribute long               screenX;
--- a/dom/interfaces/events/nsIDOMMouseScrollEvent.idl
+++ b/dom/interfaces/events/nsIDOMMouseScrollEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMMouseEvent.idl"

-[builtinclass, uuid(2bce5c03-5bed-4c22-8a6a-a3ac8f5563d7)]
+[builtinclass, uuid(00404ebe-4598-4c4e-a60a-d7491922f9db)]
 interface nsIDOMMouseScrollEvent : nsIDOMMouseEvent
 {
  const long HORIZONTAL_AXIS = 1;
--- a/dom/interfaces/events/nsIDOMMutationEvent.idl
+++ b/dom/interfaces/events/nsIDOMMutationEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMEvent.idl"

-[builtinclass, uuid(982d9800-1402-46e5-8ad2-56fb0f4905ef)]
+[builtinclass, uuid(df7e4cd9-e41f-4c8e-a764-2e3191d2f463)]
 interface nsIDOMMutationEvent : nsIDOMEvent
 {
  const unsigned short      MODIFICATION       = 1;
--- a/dom/interfaces/events/nsIDOMNotifyPaintEvent.idl
+++ b/dom/interfaces/events/nsIDOMNotifyPaintEvent.idl
@ -12,7 +12,7 @@ interface nsIDOMPaintRequestList;
 * event, which fires at a window when painting has happened in
 * that window.
 */
-[builtinclass, uuid(ef68f0d5-5b55-4198-9e59-a5e2c57d3adc)]
+[builtinclass, uuid(550f660c-65a5-4e17-b828-3dbec7c44304)]
 interface nsIDOMNotifyPaintEvent : nsIDOMEvent
 {
  /**
--- a/dom/interfaces/events/nsIDOMScrollAreaEvent.idl
+++ b/dom/interfaces/events/nsIDOMScrollAreaEvent.idl
@ -5,7 +5,7 @@

 #include "nsIDOMUIEvent.idl"

-[builtinclass, uuid(49ab3d1d-f549-4cdb-904c-f6b6d3a0ec9e)]
+[builtinclass, uuid(05aaf2cf-27c3-4d3d-9e55-4c6a4cf700ec)]
 interface nsIDOMScrollAreaEvent : nsIDOMUIEvent
 {
  // Scroll area client rect
--- a/dom/interfaces/events/nsIDOMSimpleGestureEvent.idl
+++ b/dom/interfaces/events/nsIDOMSimpleGestureEvent.idl
@ -104,7 +104,7 @@
 * consuming events.
 */

-[builtinclass, uuid(d78656ab-9d68-4f03-83f9-7c7bee071aa7)]
+[builtinclass, uuid(1b9afbf0-2cf0-4a7b-99bc-cd35dbd5b637)]
 interface nsIDOMSimpleGestureEvent : nsIDOMMouseEvent
 {
  /* Swipe direction constants */
--- a/dom/interfaces/events/nsIDOMTransitionEvent.idl
+++ b/dom/interfaces/events/nsIDOMTransitionEvent.idl
@ -11,7 +11,7 @@
 * http://dev.w3.org/csswg/css3-transitions/#transition-events-
 */

-[builtinclass, uuid(a37171e0-9f43-41ea-a25c-0b78a3329683)]
+[builtinclass, uuid(acb69403-0dcb-4db0-9ffc-8a22cc56c4eb)]
 interface nsIDOMTransitionEvent : nsIDOMEvent {
  readonly attribute DOMString           propertyName;
  readonly attribute float               elapsedTime;
--- a/dom/interfaces/events/nsIDOMUIEvent.idl
+++ b/dom/interfaces/events/nsIDOMUIEvent.idl
@ -13,7 +13,7 @@
 * http://www.w3.org/TR/DOM-Level-2-Events/
 */

-[builtinclass, uuid(d73852f8-7bd6-477d-8233-117dbf83860b)]
+[builtinclass, uuid(db058d10-1db9-4cf9-bb4c-483c304a137f)]
 interface nsIDOMUIEvent : nsIDOMEvent
 {
  readonly attribute nsIDOMWindow       view;
--- a/dom/interfaces/events/nsIDOMWheelEvent.idl
+++ b/dom/interfaces/events/nsIDOMWheelEvent.idl
@ -6,7 +6,7 @@

 #include "nsIDOMMouseEvent.idl"

-[builtinclass, uuid(86e2b577-7e61-4ed5-8ddd-c1533bf07137)]
+[builtinclass, uuid(f1ca2983-8559-43d1-be0e-1af8331755fd)]
 interface nsIDOMWheelEvent : nsIDOMMouseEvent
 {
  const unsigned long DOM_DELTA_PIXEL = 0x00;
--- a/dom/interfaces/smil/nsIDOMTimeEvent.idl
+++ b/dom/interfaces/smil/nsIDOMTimeEvent.idl
@ -13,7 +13,7 @@
 * http://www.w3.org/TR/SVG/animate.html#InterfaceTimeEvent
 */

-[builtinclass, uuid(4a5a5fa6-2783-4171-b8bb-cae4ab06e6ff)]
+[builtinclass, uuid(7a1dc95e-2c05-4171-8bde-275f094dda1d)]
 interface nsIDOMTimeEvent : nsIDOMEvent
 {
  readonly attribute long detail;
--- a/dom/interfaces/xul/nsIDOMXULCommandEvent.idl
+++ b/dom/interfaces/xul/nsIDOMXULCommandEvent.idl
@ -11,7 +11,7 @@

 #include "nsIDOMUIEvent.idl"

-[builtinclass, uuid(2d5b6e19-74bb-40af-9aac-59a1e53e3fcc)]
+[builtinclass, uuid(8aa1b009-4a88-4c85-bfba-87ee32fd789f)]
 interface nsIDOMXULCommandEvent : nsIDOMUIEvent
 {
  /**
--- a/dom/media/MediaRecorder.cpp
+++ b/dom/media/MediaRecorder.cpp
@ -1075,13 +1075,7 @@ MediaRecorder::DispatchSimpleEvent(const nsAString & aStr)
  }

  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-  rv = event->InitEvent(aStr, false, false);
-
-  if (NS_FAILED(rv)) {
-    NS_WARNING("Failed to init the error event!!!");
-    return;
-  }
-
+  event->InitEvent(aStr, false, false);
  event->SetTrusted(true);

  rv = DispatchDOMEvent(nullptr, event, nullptr, nullptr);
--- a/dom/media/TextTrackList.cpp
+++ b/dom/media/TextTrackList.cpp
@ -165,12 +165,7 @@ TextTrackList::CreateAndDispatchChangeEvent()
 {
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);

-  nsresult rv = event->InitEvent(NS_LITERAL_STRING("change"), false, false);
-  if (NS_FAILED(rv)) {
-    NS_WARNING("Failed to init the change event!");
-    return;
-  }
-
+  event->InitEvent(NS_LITERAL_STRING("change"), false, false);
  event->SetTrusted(true);

  nsCOMPtr<nsIRunnable> eventRunner = new TrackEventRunner(this, event);
--- a/dom/media/webspeech/recognition/SpeechRecognition.cpp
+++ b/dom/media/webspeech/recognition/SpeechRecognition.cpp
@ -870,9 +870,8 @@ SpeechRecognition::DispatchError(EventType aErrorType,
  RefPtr<SpeechRecognitionError> srError =
    new SpeechRecognitionError(nullptr, nullptr, nullptr);

-  ErrorResult err;
  srError->InitSpeechRecognitionError(NS_LITERAL_STRING("error"), true, false,
-                                      aErrorCode, aMessage, err);
+                                      aErrorCode, aMessage);

  RefPtr<SpeechEvent> event = new SpeechEvent(this, aErrorType);
  event->mError = srError;
--- a/dom/network/TCPServerSocket.cpp
+++ b/dom/network/TCPServerSocket.cpp
@ -159,8 +159,7 @@ TCPServerSocket::OnStopListening(nsIServerSocket* aServer, nsresult aStatus)
 {
  if (aStatus != NS_BINDING_ABORTED) {
    RefPtr<Event> event = new Event(GetOwner());
-    nsresult rv = event->InitEvent(NS_LITERAL_STRING("error"), false, false);
-    NS_ENSURE_SUCCESS(rv, rv);
+    event->InitEvent(NS_LITERAL_STRING("error"), false, false);
    event->SetTrusted(true);
    bool dummy;
    DispatchEvent(event, &dummy);
--- a/dom/notification/DesktopNotification.cpp
+++ b/dom/notification/DesktopNotification.cpp
@ -175,10 +175,7 @@ DesktopNotification::DispatchNotificationEvent(const nsString& aName)

  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
  // it doesn't bubble, and it isn't cancelable
-  nsresult rv = event->InitEvent(aName, false, false);
-  if (NS_FAILED(rv)) {
-    return;
-  }
+  event->InitEvent(aName, false, false);
  event->SetTrusted(true);
  DispatchDOMEvent(nullptr, event, nullptr, nullptr);
 }
--- a/dom/notification/Notification.cpp
+++ b/dom/notification/Notification.cpp
@ -1110,8 +1110,7 @@ Notification::DispatchClickEvent()
 {
  AssertIsOnTargetThread();
  RefPtr<Event> event = NS_NewDOMEvent(this, nullptr, nullptr);
-  nsresult rv = event->InitEvent(NS_LITERAL_STRING("click"), false, true);
-  NS_ENSURE_SUCCESS(rv, false);
+  event->InitEvent(NS_LITERAL_STRING("click"), false, true);
  event->SetTrusted(true);
  WantsPopupControlCheck popupControlCheck(event);
  bool doDefaultAction = true;
--- a/dom/smil/TimeEvent.cpp
+++ b/dom/smil/TimeEvent.cpp
@ -64,9 +64,8 @@ TimeEvent::InitTimeEvent(const nsAString& aTypeArg,
                         nsIDOMWindow* aViewArg,
                         int32_t aDetailArg)
 {
-  nsresult rv = Event::InitEvent(aTypeArg, false /*doesn't bubble*/,
-                                           false /*can't cancel*/);
-  NS_ENSURE_SUCCESS(rv, rv);
+  Event::InitEvent(aTypeArg, false /*doesn't bubble*/,
+                   false /*can't cancel*/);

  mDetail = aDetailArg;
  mView = aViewArg;
--- a/dom/smil/TimeEvent.h
+++ b/dom/smil/TimeEvent.h
@ -47,12 +47,6 @@ public:
    return mView;
  }

-  void InitTimeEvent(const nsAString& aType, nsIDOMWindow* aView,
-                     int32_t aDetail, ErrorResult& aRv)
-  {
-    aRv = InitTimeEvent(aType, aView, aDetail);
-  }
-
 private:
  ~TimeEvent() {}

--- a/dom/system/nsDeviceSensors.cpp
+++ b/dom/system/nsDeviceSensors.cpp
@ -387,15 +387,13 @@ nsDeviceSensors::FireDOMMotionEvent(nsIDOMDocument *domdoc,

  DeviceMotionEvent* me = static_cast<DeviceMotionEvent*>(event.get());

-  ErrorResult rv;
  me->InitDeviceMotionEvent(NS_LITERAL_STRING("devicemotion"),
                            true,
                            false,
                            *mLastAcceleration,
                            *mLastAccelerationIncludingGravity,
                            *mLastRotationRate,
-                            Nullable<double>(DEFAULT_SENSOR_POLL),
-                            rv);
+                            Nullable<double>(DEFAULT_SENSOR_POLL));

  event->SetTrusted(true);

--- a/dom/webidl/CompositionEvent.webidl
+++ b/dom/webidl/CompositionEvent.webidl
@ -17,7 +17,6 @@ interface CompositionEvent : UIEvent

 partial interface CompositionEvent
 {
-  [Throws]
  void initCompositionEvent(DOMString typeArg,
                            boolean canBubbleArg,
                            boolean cancelableArg,
--- a/dom/webidl/DeviceMotionEvent.webidl
+++ b/dom/webidl/DeviceMotionEvent.webidl
@ -47,7 +47,6 @@ dictionary DeviceMotionEventInit : EventInit {

 // Mozilla extensions.
 partial interface DeviceMotionEvent {
-  [Throws]
  void initDeviceMotionEvent(DOMString type,
                             boolean canBubble,
                             boolean cancelable,
--- a/dom/webidl/DeviceOrientationEvent.webidl
+++ b/dom/webidl/DeviceOrientationEvent.webidl
@ -13,7 +13,6 @@ interface DeviceOrientationEvent : Event
  readonly attribute boolean absolute;

  // initDeviceOrientationEvent is a Gecko specific deprecated method.
-  [Throws]
  void initDeviceOrientationEvent(DOMString type,
                                  boolean canBubble,
                                  boolean cancelable,
--- a/dom/webidl/DragEvent.webidl
+++ b/dom/webidl/DragEvent.webidl
@ -9,7 +9,6 @@ interface DragEvent : MouseEvent
 {
  readonly attribute DataTransfer? dataTransfer;

-  [Throws]
  void initDragEvent(DOMString type,
                     boolean canBubble,
                     boolean cancelable,
--- a/dom/webidl/Event.webidl
+++ b/dom/webidl/Event.webidl
@ -43,7 +43,6 @@ interface Event {
  [Pure]
  readonly attribute DOMHighResTimeStamp timeStamp;

-  [Throws]
  void initEvent(DOMString type, boolean bubbles, boolean cancelable);
 };

--- a/dom/webidl/HashChangeEvent.webidl
+++ b/dom/webidl/HashChangeEvent.webidl
@ -10,7 +10,6 @@ interface HashChangeEvent : Event
  readonly attribute DOMString? oldURL;
  readonly attribute DOMString? newURL;

-  [Throws]
  void initHashChangeEvent(DOMString typeArg,
                           boolean canBubbleArg,
                           boolean cancelableArg,
--- a/dom/webidl/KeyEvent.webidl
+++ b/dom/webidl/KeyEvent.webidl
@ -224,7 +224,6 @@ interface KeyEvent
  // for compatibility with the other web browsers on Windows.
  const unsigned long DOM_VK_WIN_OEM_CLEAR  = 0xFE;

-  [Throws]
  void initKeyEvent(DOMString type,
                    boolean canBubble,
                    boolean cancelable,
--- a/dom/webidl/MessageEvent.webidl
+++ b/dom/webidl/MessageEvent.webidl
@ -42,7 +42,6 @@ interface MessageEvent : Event {
   */
  readonly attribute MessagePortList? ports;

-  [Throws]
  void initMessageEvent(DOMString type, boolean bubbles, boolean cancelable,
                        any data, DOMString origin, DOMString lastEventId,
                        (WindowProxy or MessagePort)? source,
--- a/dom/webidl/MouseEvent.webidl
+++ b/dom/webidl/MouseEvent.webidl
@ -32,7 +32,6 @@ interface MouseEvent : UIEvent {
  readonly attribute long           movementY;

  // Deprecated in DOM Level 3:
-  [Throws]
  void                              initMouseEvent(DOMString typeArg, 
                                                   boolean canBubbleArg, 
                                                   boolean cancelableArg, 
@ -91,7 +90,6 @@ partial interface MouseEvent

  readonly attribute unsigned short mozInputSource;

-  [Throws]
  void                initNSMouseEvent(DOMString typeArg,
                                       boolean canBubbleArg,
                                       boolean cancelableArg,
--- a/dom/webidl/MouseScrollEvent.webidl
+++ b/dom/webidl/MouseScrollEvent.webidl
@ -11,7 +11,6 @@ interface MouseScrollEvent : MouseEvent

  readonly attribute long axis;

-  [Throws]
  void initMouseScrollEvent(DOMString type,
                            boolean canBubble,
                            boolean cancelable,
--- a/dom/webidl/ScrollAreaEvent.webidl
+++ b/dom/webidl/ScrollAreaEvent.webidl
@ -11,7 +11,6 @@ interface ScrollAreaEvent : UIEvent
  readonly attribute float width;
  readonly attribute float height;

-  [Throws]
  void initScrollAreaEvent(DOMString type,
                           boolean canBubble,
                           boolean cancelable,
--- a/dom/webidl/SimpleGestureEvent.webidl
+++ b/dom/webidl/SimpleGestureEvent.webidl
@ -24,7 +24,6 @@ interface SimpleGestureEvent : MouseEvent

  readonly attribute unsigned long clickCount;

-  [Throws]
  void initSimpleGestureEvent(DOMString typeArg,
                              boolean canBubbleArg,
                              boolean cancelableArg,
--- a/dom/webidl/StorageEvent.webidl
+++ b/dom/webidl/StorageEvent.webidl
@ -20,7 +20,6 @@ interface StorageEvent : Event
  readonly attribute Storage? storageArea;

  // Bug 1016053 - This is not spec compliant.
-  [Throws]
  void initStorageEvent(DOMString type,
                        boolean canBubble,
                        boolean cancelable,
--- a/dom/webidl/TouchEvent.webidl
+++ b/dom/webidl/TouchEvent.webidl
@ -15,7 +15,6 @@ interface TouchEvent : UIEvent {
  readonly attribute boolean ctrlKey;
  readonly attribute boolean shiftKey;

-  [Throws]
  void initTouchEvent(DOMString type,
                      boolean canBubble,
                      boolean cancelable,
--- a/dom/webidl/XULCommandEvent.webidl
+++ b/dom/webidl/XULCommandEvent.webidl
@ -14,7 +14,6 @@ interface XULCommandEvent : UIEvent

  readonly attribute Event? sourceEvent;

-  [Throws]
  void initCommandEvent(DOMString type,
                        boolean canBubble,
                        boolean cancelable,
--- a/dom/workers/ServiceWorkerMessageEvent.cpp
+++ b/dom/workers/ServiceWorkerMessageEvent.cpp
@ -142,10 +142,7 @@ ServiceWorkerMessageEvent::Constructor(EventTarget* aEventTarget,
  RefPtr<ServiceWorkerMessageEvent> event =
    new ServiceWorkerMessageEvent(aEventTarget, nullptr, nullptr);

-  aRv = event->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
-  if (NS_WARN_IF(aRv.Failed())) {
-    return nullptr;
-  }
+  event->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);

  bool trusted = event->Init(aEventTarget);
  event->SetTrusted(trusted);
--- a/dom/workers/WorkerPrivate.cpp
+++ b/dom/workers/WorkerPrivate.cpp
@ -572,12 +572,7 @@ private:

    RefPtr<Event> event = NS_NewDOMEvent(globalScope, nullptr, nullptr);

-    nsresult rv = event->InitEvent(NS_LITERAL_STRING("close"), false, false);
-    if (NS_FAILED(rv)) {
-      Throw(aCx, rv);
-      return false;
-    }
-
+    event->InitEvent(NS_LITERAL_STRING("close"), false, false);
    event->SetTrusted(true);

    globalScope->DispatchDOMEvent(nullptr, event, nullptr, nullptr);
@ -3073,9 +3068,7 @@ WorkerPrivate::OfflineStatusChangeEventInternal(JSContext* aCx, bool aIsOffline)

  RefPtr<Event> event = NS_NewDOMEvent(globalScope, nullptr, nullptr);

-  nsresult rv = event->InitEvent(eventType, false, false);
-  NS_ENSURE_SUCCESS_VOID(rv);
-
+  event->InitEvent(eventType, false, false);
  event->SetTrusted(true);

  globalScope->DispatchDOMEvent(nullptr, event, nullptr, nullptr);
--- a/embedding/components/windowwatcher/nsAutoWindowStateHelper.cpp
+++ b/embedding/components/windowwatcher/nsAutoWindowStateHelper.cpp
@ -61,9 +61,7 @@ nsAutoWindowStateHelper::DispatchEventToChrome(const char* aEventName)
  if (rv.Failed()) {
    return false;
  }
-  NS_ENSURE_TRUE(NS_SUCCEEDED(event->InitEvent(
-                   NS_ConvertASCIItoUTF16(aEventName), true, true)),
-                 false);
+  event->InitEvent(NS_ConvertASCIItoUTF16(aEventName), true, true);
  event->SetTrusted(true);
  event->GetInternalNSEvent()->mFlags.mOnlyChromeDispatch = true;

--- a/layout/base/nsDocumentViewer.cpp
+++ b/layout/base/nsDocumentViewer.cpp
@ -1064,6 +1064,7 @@ nsDocumentViewer::PermitUnloadInternal(bool *aShouldPrompt,
 {
  AutoDontWarnAboutSyncXHR disableSyncXHRWarning;

+  nsresult rv = NS_OK;
  *aPermitUnload = true;

  if (!mDocument
@ -1103,9 +1104,7 @@ nsDocumentViewer::PermitUnloadInternal(bool *aShouldPrompt,
                      getter_AddRefs(event));
  nsCOMPtr<nsIDOMBeforeUnloadEvent> beforeUnload = do_QueryInterface(event);
  NS_ENSURE_STATE(beforeUnload);
-  nsresult rv = event->InitEvent(NS_LITERAL_STRING("beforeunload"),
-                                 false, true);
-  NS_ENSURE_SUCCESS(rv, rv);
+  event->InitEvent(NS_LITERAL_STRING("beforeunload"), false, true);

  // Dispatching to |window|, but using |document| as the target.
  event->SetTarget(mDocument);