Bug 862240 - Add null checking and reset the runnable member pointer when entering runnable method. r=drs

gfx/layers/ipc/GestureEventListener.cpp

@@ -142,7 +142,7 @@ nsEventStatus GestureEventListener::HandleInputEvent(const InputData& aEvent)
           event.mTime - mLastTapEndTime > MAX_TAP_TIME) {
         // mDoubleTapTimeoutTask wasn't scheduled in time. We need to run the
         // task synchronously to confirm the last tap.
-        mDoubleTapTimeoutTask->Cancel();
+        CancelDoubleTapTimeoutTask();
         TimeoutDoubleTap();
 
         // Change the state so we can proceed to process the current tap.
@@ -150,14 +150,12 @@ nsEventStatus GestureEventListener::HandleInputEvent(const InputData& aEvent)
       }
 
       if (mState == GESTURE_WAITING_DOUBLE_TAP) {
-        mDoubleTapTimeoutTask->Cancel();
-
+        CancelDoubleTapTimeoutTask();
         // We were waiting for a double tap and it has arrived.
         HandleDoubleTap(event);
         mState = GESTURE_NONE;
       } else if (mState == GESTURE_WAITING_SINGLE_TAP) {
-        mLongTapTimeoutTask->Cancel();
-
+        CancelLongTapTimeoutTask();
         HandleSingleTapUpEvent(event);
 
         // We were not waiting for anything but a single tap has happened that
@@ -299,7 +297,7 @@ nsEventStatus GestureEventListener::HandleTapCancel(const MultiTouchInput& aEven
   switch (mState)
   {
   case GESTURE_WAITING_SINGLE_TAP:
-    mLongTapTimeoutTask->Cancel();
+    CancelLongTapTimeoutTask();
     mState = GESTURE_NONE;
     break;
 
@@ -321,6 +319,7 @@ nsEventStatus GestureEventListener::HandleDoubleTap(const MultiTouchInput& aEven
 
 void GestureEventListener::TimeoutDoubleTap()
 {
+  mDoubleTapTimeoutTask = nullptr;
   // If we haven't gotten another tap by now, reset the state and treat it as a
   // single tap. It couldn't have been a double tap.
   if (mState == GESTURE_WAITING_DOUBLE_TAP) {
@@ -330,8 +329,16 @@ void GestureEventListener::TimeoutDoubleTap()
   }
 }
 
+void GestureEventListener::CancelDoubleTapTimeoutTask() {
+  if (mDoubleTapTimeoutTask) {
+    mDoubleTapTimeoutTask->Cancel();
+    mDoubleTapTimeoutTask = nullptr;
+  }
+}
+
 void GestureEventListener::TimeoutLongTap()
 {
+  mLongTapTimeoutTask = nullptr;
   // If the tap has not been released, this is a long press.
   if (mState == GESTURE_WAITING_SINGLE_TAP) {
     mState = GESTURE_NONE;
@@ -340,6 +347,13 @@ void GestureEventListener::TimeoutLongTap()
   }
 }
 
+void GestureEventListener::CancelLongTapTimeoutTask() {
+  if (mLongTapTimeoutTask) {
+    mLongTapTimeoutTask->Cancel();
+    mLongTapTimeoutTask = nullptr;
+  }
+}
+
 AsyncPanZoomController* GestureEventListener::GetAsyncPanZoomController() {
   return mAsyncPanZoomController;
 }

gfx/layers/ipc/GestureEventListener.h

@@ -201,15 +201,21 @@ protected:
    * Task used to timeout a double tap. This gets posted to the UI thread such
    * that it runs a short time after a single tap happens. We cache it so that
    * we can cancel it if a double tap actually comes in.
+   * CancelDoubleTapTimeoutTask: Cancel the mDoubleTapTimeoutTask and also set
+   * it to null.
    */
   CancelableTask *mDoubleTapTimeoutTask;
+  inline void CancelDoubleTapTimeoutTask();
 
   /**
    * Task used to timeout a long tap. This gets posted to the UI thread such
    * that it runs a time when a single tap happens. We cache it so that
    * we can cancel it if any other touch event happens.
+   * CancelLongTapTimeoutTask: Cancel the mLongTapTimeoutTask and also set
+   * it to null.
    */
   CancelableTask *mLongTapTimeoutTask;
+  inline void CancelLongTapTimeoutTask();
 
   /**
    * Position of the last touch starting. This is only valid during an attempt