Bug 1048888 - Initialize member variables to nullptr. r=botond

gfx/layers/apz/src/GestureEventListener.cpp

@@ -54,7 +54,9 @@ GestureEventListener::GestureEventListener(AsyncPanZoomController* aAsyncPanZoom
     mState(GESTURE_NONE),
     mSpanChange(0.0f),
     mPreviousSpan(0.0f),
-    mLastTouchInput(MultiTouchInput::MULTITOUCH_START, 0, TimeStamp(), 0)
+    mLastTouchInput(MultiTouchInput::MULTITOUCH_START, 0, TimeStamp(), 0),
+    mLongTapTimeoutTask(nullptr),
+    mMaxTapTimeoutTask(nullptr)
 {
 }