Make tapDown async.

content/browser/renderer_host/input/gesture_event_filter.cc

Index: content/browser/renderer_host/input/gesture_event_filter.cc
diff --git a/content/browser/renderer_host/input/gesture_event_filter.cc b/content/browser/renderer_host/input/gesture_event_filter.cc
index 9a80a06b4ffade3b286d785690c46c528f0d118f..d0ca86a6f0348a3930cec03599ffb1b6f02865a0 100644
--- a/content/browser/renderer_host/input/gesture_event_filter.cc
+++ b/content/browser/renderer_host/input/gesture_event_filter.cc
@@ -239,10 +239,17 @@ bool GestureEventFilter::ShouldForwardForCoalescing(
       break;
   }
   coalesced_gesture_events_.push_back(gesture_event);
+
+  // Ensure that if the added event is asynchonous, it is fired and
+  // removed from |coalesced_gesture_events_|.
+  SendAsynchEvents();
   return ShouldHandleEventNow();
 }
 
 void GestureEventFilter::ProcessGestureAck(bool processed, int type) {
+  if (IsGestureEventTypeAsync(type))
+    return;

[jdduke (slow), 2013/09/30 15:42:56]

As I mention below, we might be able to use a return value here and have the GEF
take be the sole checker of this condition.

+
   if (coalesced_gesture_events_.empty()) {
     DLOG(ERROR) << "Received unexpected ACK for event type " << type;
     return;
@@ -256,6 +263,9 @@ void GestureEventFilter::ProcessGestureAck(bool processed, int type) {
       touchpad_tap_suppression_controller_->GestureFlingCancelAck(processed);
   }
   coalesced_gesture_events_.pop_front();
+  // If the event which was just ACKed was blocking asynchronous
+  // events, fire those asynchronous events now.
+  SendAsynchEvents();
   if (ignore_next_ack_) {
     ignore_next_ack_ = false;
   } else if (!coalesced_gesture_events_.empty()) {
@@ -436,4 +446,23 @@ gfx::Transform GestureEventFilter::GetTransformForEvent(
   }
   return gesture_transform;
 }
+
+void GestureEventFilter::SendAsynchEvents() {
+  GestureEventWithLatencyInfo gesture_event;
+  while (!coalesced_gesture_events_.empty()) {
+    if (GestureEventFilter::IsGestureEventTypeAsync(

[jochen (gone - plz use gerrit), 2013/09/30 15:19:03]

nit. can you invert the condition so you can return early? i.e.

gesture_event = coalesced_gesture_events_.front();
if (!GestureEventFilter::IsGestureEventTypeAsync(gesture_event))
  return;

[tdresser, 2013/09/30 15:34:48]

Good call, thanks. Done.

[jdduke (slow), 2013/09/30 15:42:56]

+1

+            coalesced_gesture_events_.front().event.type)) {
+      gesture_event = coalesced_gesture_events_.front();
+      coalesced_gesture_events_.pop_front();
+      input_router_->SendGestureEventImmediately(gesture_event);
+    } else {
+      return;
+    }
+  }
+}
+
+bool GestureEventFilter::IsGestureEventTypeAsync(int type) {
+  return type == WebInputEvent::GestureTapDown;
+}
+
 }  // namespace content