Bug 1140578 - Add a explicit flag to track if we have pending touch moves to process. r=mchang

widget/gonk/GeckoTouchDispatcher.cpp

@@ -63,6 +63,7 @@ GeckoTouchDispatcher::GetInstance()
 
 GeckoTouchDispatcher::GeckoTouchDispatcher()
   : mTouchQueueLock("GeckoTouchDispatcher::mTouchQueueLock")
+  , mHavePendingTouchMoves(false)
   , mTouchEventsFiltered(false)
 {
   // Since GeckoTouchDispatcher is initialized when input is initialized
@@ -112,6 +113,7 @@ GeckoTouchDispatcher::NotifyTouch(MultiTouchInput& aTouch, TimeStamp aEventTime)
   if (aTouch.mType == MultiTouchInput::MULTITOUCH_MOVE) {
     MutexAutoLock lock(mTouchQueueLock);
     mTouchMoveEvents.push_back(aTouch);
+    mHavePendingTouchMoves = true;
     if (mResamplingEnabled) {
       return;
     }
@@ -131,9 +133,10 @@ GeckoTouchDispatcher::DispatchTouchMoveEvents(TimeStamp aVsyncTime)
 
   {
     MutexAutoLock lock(mTouchQueueLock);
-    if (mTouchMoveEvents.empty()) {
+    if (!mHavePendingTouchMoves) {
       return;
     }
+    mHavePendingTouchMoves = false;
 
     if (mResamplingEnabled) {
       int touchCount = mTouchMoveEvents.size();

widget/gonk/GeckoTouchDispatcher.h

@@ -60,10 +60,12 @@ private:
   void DispatchMouseEvent(MultiTouchInput& aMultiTouch,
                           bool aForwardToChildren);
 
-  // mTouchQueueLock are used to protect the vector below
-  // as it is accessed on the vsync thread and main thread
+  // mTouchQueueLock is used to protect the vector and state below
+  // as it is accessed on multiple threads.
   Mutex mTouchQueueLock;
   std::vector<MultiTouchInput> mTouchMoveEvents;
+  bool mHavePendingTouchMoves;
+  // end stuff protected by mTouchQueueLock
 
   bool mResamplingEnabled;
   bool mTouchEventsFiltered;