Support vsync-aligned wheel event dispatch

content/browser/renderer_host/input/input_router_impl.h

Index: content/browser/renderer_host/input/input_router_impl.h
diff --git a/content/browser/renderer_host/input/input_router_impl.h b/content/browser/renderer_host/input/input_router_impl.h
index 189d93ddd047fa2aa730ab2647ea2d952969c9ae..67d71a45bed4f4971c6f056f28b3d8f2d098c375 100644
--- a/content/browser/renderer_host/input/input_router_impl.h
+++ b/content/browser/renderer_host/input/input_router_impl.h
@@ -9,13 +9,13 @@
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
-#include "base/memory/scoped_vector.h"
 #include "base/time/time.h"
 #include "content/browser/renderer_host/input/gesture_event_queue.h"
 #include "content/browser/renderer_host/input/input_router.h"
 #include "content/browser/renderer_host/input/touch_action_filter.h"
 #include "content/browser/renderer_host/input/touch_event_queue.h"
 #include "content/browser/renderer_host/input/touchpad_tap_suppression_controller.h"
+#include "content/browser/renderer_host/input/wheel_event_queue.h"
 #include "content/common/input/input_event_stream_validator.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 
@@ -40,12 +40,14 @@ class CONTENT_EXPORT InputRouterImpl
     : public NON_EXPORTED_BASE(InputRouter),
       public NON_EXPORTED_BASE(GestureEventQueueClient),
       public NON_EXPORTED_BASE(TouchEventQueueClient),
-      public NON_EXPORTED_BASE(TouchpadTapSuppressionControllerClient) {
+      public NON_EXPORTED_BASE(TouchpadTapSuppressionControllerClient),
+      public NON_EXPORTED_BASE(WheelEventQueueClient) {
  public:
   struct CONTENT_EXPORT Config {
     Config();
     GestureEventQueue::Config gesture_config;
     TouchEventQueue::Config touch_config;
+    bool buffer_wheel_events_until_flush;
   };
 
   InputRouterImpl(IPC::Sender* sender,
@@ -86,14 +88,21 @@ private:
   void OnTouchEventAck(const TouchEventWithLatencyInfo& event,
                        InputEventAckState ack_result) override;
 
-  // GetureEventFilterClient
+  // GestureEventQueueClient
   void SendGestureEventImmediately(
       const GestureEventWithLatencyInfo& gesture_event) override;
   void OnGestureEventAck(const GestureEventWithLatencyInfo& event,
                          InputEventAckState ack_result) override;
 
-  bool SendMoveCaret(scoped_ptr<IPC::Message> message);
+  // WheelEventQueueClient
+  void SendWheelEventImmediately(
+      const MouseWheelEventWithLatencyInfo& wheel_event) override;
+  void OnWheelEventAck(const MouseWheelEventWithLatencyInfo& event,
+                       InputEventAckState ack_result) override;
+  void SetNeedsFlush() override;
+
   bool SendSelectMessage(scoped_ptr<IPC::Message> message);
+  bool SendMoveCaret(scoped_ptr<IPC::Message> message);
   bool Send(IPC::Message* message);
 
   // Filters and forwards |input_event| to the appropriate handler.
@@ -209,21 +218,6 @@ private:
   scoped_ptr<MouseEventWithLatencyInfo> next_mouse_move_;
   MouseEventWithLatencyInfo current_mouse_move_;
 
-  // (Similar to |mouse_move_pending_|.) True if a mouse wheel event was sent
-  // and we are waiting for a corresponding ack.
-  bool mouse_wheel_pending_;
-  MouseWheelEventWithLatencyInfo current_wheel_event_;
-
-  // (Similar to |next_mouse_move_|.) The next mouse wheel events to send.
-  // Unlike mouse moves, mouse wheel events received while one is pending are
-  // coalesced (by accumulating deltas) if they match the previous event in
-  // modifiers. On the Mac, in particular, mouse wheel events are received at a
-  // high rate; not waiting for the ack results in jankiness, and using the same
-  // mechanism as for mouse moves (just dropping old events when multiple ones
-  // would be queued) results in very slow scrolling.
-  typedef std::deque<MouseWheelEventWithLatencyInfo> WheelEventQueue;
-  WheelEventQueue coalesced_mouse_wheel_events_;
-
   // A queue of keyboard events. We can't trust data from the renderer so we
   // stuff key events into a queue and pop them out on ACK, feeding our copy
   // back to whatever unhandled handler instead of the returned version.
@@ -248,6 +242,7 @@ private:
 
   TouchEventQueue touch_event_queue_;
   GestureEventQueue gesture_event_queue_;
+  WheelEventQueue wheel_event_queue_;
   TouchActionFilter touch_action_filter_;
   InputEventStreamValidator input_stream_validator_;
   InputEventStreamValidator output_stream_validator_;