Coalesce async touch move events until the ack back from render

content/browser/renderer_host/input/touch_event_queue.cc

Index: content/browser/renderer_host/input/touch_event_queue.cc
diff --git a/content/browser/renderer_host/input/touch_event_queue.cc b/content/browser/renderer_host/input/touch_event_queue.cc
index b766b3d1b51530ec4b49d9685cde78ebb302b525..b8af78f43443977c1867ae959f3a0a0418842891 100644
--- a/content/browser/renderer_host/input/touch_event_queue.cc
+++ b/content/browser/renderer_host/input/touch_event_queue.cc
@@ -372,7 +372,8 @@ TouchEventQueue::TouchEventQueue(TouchEventQueueClient* client,
       drop_remaining_touches_in_sequence_(false),
       touchmove_slop_suppressor_(new TouchMoveSlopSuppressor),
       send_touch_events_async_(false),
-      last_sent_touch_timestamp_sec_(0) {
+      last_sent_touch_timestamp_sec_(0),
+      receiving_async_touch_move_ack_(false) {
   DCHECK(client);
   if (config.touch_ack_timeout_supported) {
     timeout_handler_.reset(
@@ -434,7 +435,11 @@ void TouchEventQueue::ProcessTouchAck(InputEventAckState ack_result,
   if (touch_queue_.empty())
     return;
 
-  PopTouchEventToClient(ack_result, latency_info);
+  // If we receive the ACK from render for async touch moves, we do not call
+  // this function again, because it has already been called by the fake ACK.
+  if(!receiving_async_touch_move_ack_)
+    PopTouchEventToClient(ack_result, latency_info);
+
   TryForwardNextEventToRenderer();
 }
 
@@ -480,7 +485,9 @@ void TouchEventQueue::ForwardNextEventToRenderer() {
         touch.event.timeStampSeconds >=
         last_sent_touch_timestamp_sec_ + kAsyncTouchMoveIntervalSec;
 
-    if (!send_touchmove_now) {
+    // We send the next async touchmove after an interval of
+    // kAsyncTouchMoveIntervalSec and receive the ACK back from render.
+    if (!send_touchmove_now || !receiving_async_touch_move_ack_) {
       if (!pending_async_touchmove_) {
         pending_async_touchmove_.reset(new TouchEventWithLatencyInfo(touch));
       } else {
@@ -496,6 +503,8 @@ void TouchEventQueue::ForwardNextEventToRenderer() {
       TryForwardNextEventToRenderer();
       return;
     }
+
+    receiving_async_touch_move_ack_ = false;
   }
 
   last_sent_touch_timestamp_sec_ = touch.event.timeStampSeconds;