Bug 1142437 - Better deal with delayed state change notifications from APZ. r=botond

gfx/layers/apz/util/APZEventState.cpp

@@ -282,7 +282,7 @@ APZEventState::ProcessTouchEvent(const WidgetTouchEvent& aEvent,
     }
     // fall through
   case NS_TOUCH_CANCEL:
-    mActiveElementManager->HandleTouchEnd(mEndTouchIsClick);
+    mActiveElementManager->HandleTouchEndEvent(mEndTouchIsClick);
     // fall through
   case NS_TOUCH_MOVE: {
     SendPendingTouchPreventedResponse(isTouchPrevented, aGuid);
@@ -365,6 +365,7 @@ APZEventState::ProcessAPZStateChange(const nsCOMPtr<nsIDocument>& aDocument,
   case APZStateChange::EndTouch:
   {
     mEndTouchIsClick = aArg;
+    mActiveElementManager->HandleTouchEnd();
     break;
   }
   default:

gfx/layers/apz/util/ActiveElementManager.cpp

@@ -109,9 +109,9 @@ ActiveElementManager::HandlePanStart()
 }
 
 void
-ActiveElementManager::HandleTouchEnd(bool aWasClick)
+ActiveElementManager::HandleTouchEndEvent(bool aWasClick)
 {
-  AEM_LOG("Touch end, aWasClick: %d\n", aWasClick);
+  AEM_LOG("Touch end event, aWasClick: %d\n", aWasClick);
 
   // If the touch was a click, make mTarget :active right away.
   // nsEventStateManager will reset the active element when processing
@@ -129,6 +129,13 @@ ActiveElementManager::HandleTouchEnd(bool aWasClick)
   ResetTouchBlockState();
 }
 
+void
+ActiveElementManager::HandleTouchEnd()
+{
+  AEM_LOG("Touch end, clearing pan state\n");
+  mCanBePanSet = false;
+}
+
 bool
 ActiveElementManager::ActiveElementUsesStyle() const
 {

gfx/layers/apz/util/ActiveElementManager.h

@@ -33,14 +33,15 @@ public:
 
   /**
    * Specify the target of a touch. Typically this should be called right
-   * before HandleTouchStart(), but we give callers the flexibility to specify
-   * the target later if they don't know it at the time they call
-   * HandleTouchStart().
+   * after HandleTouchStart(), but in cases where the APZ needs to wait for
+   * a content response the HandleTouchStart() may be delayed, in which case
+   * this function can be called first.
    * |aTarget| may be nullptr.
    */
   void SetTargetElement(dom::EventTarget* aTarget);
   /**
-   * Handle a touch-start event.
+   * Handle a touch-start state notification from APZ. This notification
+   * may be delayed until after touch listeners have responded to the APZ.
    * @param aCanBePan whether the touch can be a pan
    */
   void HandleTouchStart(bool aCanBePan);
@@ -52,7 +53,12 @@ public:
    * Handle a touch-end or touch-cancel event.
    * @param aWasClick whether the touch was a click
    */
-  void HandleTouchEnd(bool aWasClick);
+  void HandleTouchEndEvent(bool aWasClick);
+  /**
+   * Handle a touch-end state notification from APZ. This notification may be
+   * delayed until after touch listeners have responded to the APZ.
+   */
+  void HandleTouchEnd();
   /**
    * @return true iff the currently active element (or one of its ancestors)
    * actually had a style for the :active pseudo-class. The currently active