Bug 1315862 Part1: Stop dispatching pointer events in the system group. r=masayuki,smaug

MozReview-Commit-ID: 8Xqp3bxlRFt

--HG--
extra : rebase_source : 25afbefb19e5ae613e9e493ea2f275a36004d523

dom/events/EventDispatcher.cpp

@@ -407,7 +407,8 @@ EventTargetChainItem::HandleEventTargetChain(
   }
   aVisitor.mEvent->mFlags.mInBubblingPhase = false;
 
-  if (!aVisitor.mEvent->mFlags.mInSystemGroup) {
+  if (!aVisitor.mEvent->mFlags.mInSystemGroup &&
+      aVisitor.mEvent->IsAllowedToDispatchInSystemGroup()) {
     // Dispatch to the system event group.  Make sure to clear the
     // STOP_DISPATCH flag since this resets for each event group.
     aVisitor.mEvent->mFlags.mPropagationStopped = false;

widget/BasicEvents.h

@@ -553,6 +553,10 @@ public:
    * Whether the event should cause a DOM event.
    */
   bool IsAllowedToDispatchDOMEvent() const;
+  /**
+   * Whether the event should be dispatched in system group.
+   */
+  bool IsAllowedToDispatchInSystemGroup() const;
   /**
    * Initialize mComposed
    */

widget/WidgetEventImpl.cpp

@@ -416,6 +416,15 @@ WidgetEvent::IsAllowedToDispatchDOMEvent() const
   }
 }
 
+bool
+WidgetEvent::IsAllowedToDispatchInSystemGroup() const
+{
+  // We don't expect to implement default behaviors with pointer events because
+  // if we do, prevent default on mouse events can't prevent default behaviors
+  // anymore.
+  return mClass != ePointerEventClass;
+}
+
 /******************************************************************************
  * mozilla::WidgetInputEvent
  ******************************************************************************/