diff -r 000000000000 -r 6474c204b198 dom/events/AsyncEventDispatcher.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dom/events/AsyncEventDispatcher.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_AsyncEventDispatcher_h_
+#define mozilla_AsyncEventDispatcher_h_
+
+#include "mozilla/Attributes.h"
+#include "nsCOMPtr.h"
+#include "nsIDocument.h"
+#include "nsIDOMEvent.h"
+#include "nsINode.h"
+#include "nsString.h"
+#include "nsThreadUtils.h"
+
+namespace mozilla {
+
+/**
+ * Use nsAsyncDOMEvent to fire a DOM event that requires safe a stable DOM.
+ * For example, you may need to fire an event from within layout, but
+ * want to ensure that the event handler doesn't mutate the DOM at
+ * the wrong time, in order to avoid resulting instability.
+ */
+ 
+class AsyncEventDispatcher : public nsRunnable
+{
+public:
+  AsyncEventDispatcher(nsINode* aEventNode, const nsAString& aEventType,
+                       bool aBubbles, bool aDispatchChromeOnly)
+    : mEventNode(aEventNode)
+    , mEventType(aEventType)
+    , mBubbles(aBubbles)
+    , mDispatchChromeOnly(aDispatchChromeOnly)
+  {
+  }
+
+  AsyncEventDispatcher(nsINode* aEventNode, nsIDOMEvent* aEvent)
+    : mEventNode(aEventNode)
+    , mEvent(aEvent)
+    , mDispatchChromeOnly(false)
+  {
+  }
+
+  AsyncEventDispatcher(nsINode* aEventNode, WidgetEvent& aEvent);
+
+  NS_IMETHOD Run() MOZ_OVERRIDE;
+  nsresult PostDOMEvent();
+  void RunDOMEventWhenSafe();
+
+  nsCOMPtr<nsINode>     mEventNode;
+  nsCOMPtr<nsIDOMEvent> mEvent;
+  nsString              mEventType;
+  bool                  mBubbles;
+  bool                  mDispatchChromeOnly;
+};
+
+class LoadBlockingAsyncEventDispatcher MOZ_FINAL : public AsyncEventDispatcher
+{
+public:
+  LoadBlockingAsyncEventDispatcher(nsINode* aEventNode,
+                                   const nsAString& aEventType,
+                                   bool aBubbles, bool aDispatchChromeOnly)
+    : AsyncEventDispatcher(aEventNode, aEventType,
+                           aBubbles, aDispatchChromeOnly)
+    , mBlockedDoc(aEventNode->OwnerDoc())
+  {
+    if (mBlockedDoc) {
+      mBlockedDoc->BlockOnload();
+    }
+  }
+
+  LoadBlockingAsyncEventDispatcher(nsINode* aEventNode, nsIDOMEvent* aEvent)
+    : AsyncEventDispatcher(aEventNode, aEvent)
+    , mBlockedDoc(aEventNode->OwnerDoc())
+  {
+    if (mBlockedDoc) {
+      mBlockedDoc->BlockOnload();
+    }
+  }
+  
+  ~LoadBlockingAsyncEventDispatcher();
+
+private:
+  nsCOMPtr<nsIDocument> mBlockedDoc;
+};
+
+} // namespace mozilla
+
+#endif // mozilla_AsyncEventDispatcher_h_