Defer GestureTapDown events briefly.

content/browser/renderer_host/gesture_event_filter.h

Index: content/browser/renderer_host/gesture_event_filter.h
diff --git a/content/browser/renderer_host/gesture_event_filter.h b/content/browser/renderer_host/gesture_event_filter.h
index aff3b318e35ebde4b9d0f5e3cb36b530e6634750..fc65630ec395399554a5b8cd0c7acdab28951e70 100644
--- a/content/browser/renderer_host/gesture_event_filter.h
+++ b/content/browser/renderer_host/gesture_event_filter.h
@@ -9,6 +9,8 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/time.h"
+#include "base/timer.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
 
 class MockRenderWidgetHost;
@@ -48,32 +50,50 @@ class GestureEventFilter {
  private:
   friend class ::MockRenderWidgetHost;
 
+  // Invoked on the expiration of the timer to release a deferred
+  // GestureTapDown to the renderer.
+  void SendGestureTapDownNow();
+
   // Returns |true| if the given GestureFlingCancel should be discarded
   // as unnecessary.
   bool ShouldDiscardFlingCancelEvent(
     const WebKit::WebGestureEvent& gesture_event);
 
+  // Return true if the only event in the queue is the current event and
+  // hence that event should be handled now.
+  bool ShouldHandleEventNow();
+
+  // Merge a GestureScrollUpdate into the queue if possible or append
+  // it to the queue.
+  void MergeOrInsertScrollEvent(
+       const WebKit::WebGestureEvent& gesture_event);
+
   // Only a RenderWidgetHostViewImpl can own an instance.
   RenderWidgetHostImpl* render_widget_host_;
 
-  // True if a GestureFlingStart is in progress on the renderer.
+  // True if a GestureFlingStart is in progress on the renderer or
+  // queued without a subsequent queued GestureFlingCancel event.
   bool fling_in_progress_;
 
-  // (Similar to |mouse_wheel_pending_|.). True if gesture event was sent and
-  // we are waiting for a corresponding ack.
-  bool gesture_event_pending_;
+  // Timer to release a previously deferred GestureTapDown event.
+  base::OneShotTimer<GestureEventFilter> send_gtd_timer_;
 
   // An object tracking the state of touchpad action on the delivery of mouse
-  // events to the renderer to filter mouse actiosn immediately after a touchpad
+  // events to the renderer to filter mouse  immediately after a touchpad
   // fling canceling tap.
   scoped_ptr<TapSuppressionController> tap_suppression_controller_;
 
   typedef std::deque<WebKit::WebGestureEvent> GestureEventQueue;
 
-  // (Similar to |coalesced_mouse_wheel_events_|.) GestureScrollUpdate events
-  // are coalesced by merging deltas in a similar fashion as wheel events.
+  // Queue of coalesced gesture events not yet sent to the renderer.
   GestureEventQueue coalesced_gesture_events_;
 
+  // Tap gesture event currently subject to deferral.
+  WebKit::WebGestureEvent deferred_tap_down_event_;
+
+  // Time window in which to defer a GestureTapDown.
+  int maximum_tap_gap_time_ms_;
+
   DISALLOW_COPY_AND_ASSIGN(GestureEventFilter);
 };