[VSync Queue] Flush input in CommitComplete()

cc/input/input_handler.h

Index: cc/input/input_handler.h
diff --git a/cc/input/input_handler.h b/cc/input/input_handler.h
index 6ffdcce57374f0effc35fac58535839c62b981a2..c39c48bcf3dbf9e4b9b948f66f2a2ac50efe9bd5 100644
--- a/cc/input/input_handler.h
+++ b/cc/input/input_handler.h
@@ -110,12 +110,21 @@ class CC_EXPORT InputHandler {
     HANDLER_ON_SCROLLING_LAYER
   };
 
+  enum class InputHandlerState {

[dtapuska, 2017/04/27 16:24:44]

This name seems a bit too generic.

[chongz, 2017/04/27 19:12:14]

Changed to READY_FOR_INPUT and BUSY_INSIDE_IMPL_FRAME, or do you have other
suggestions?

[chongz, 2017/04/28 19:21:21]

Changed enum name to |ImplThreadPhase|.

+    IDLE,
+    INSIDE_IMPL_FRAME,
+  };
+
   // Binds a client to this handler to receive notifications. Only one client
   // can be bound to an InputHandler. The client must live at least until the
   // handler calls WillShutdown() on the client.
   virtual void BindToClient(InputHandlerClient* client,
                             bool wheel_scroll_latching_enabled) = 0;
 
+  // |InputHandlerClient| should avoid delivering input events during
+  // |INSIDE_IMPL_FRAME| to reduce checkerboard issue.
+  virtual InputHandlerState GetInputHandlerState() const = 0;
+
   // Selects a layer to be scrolled using the |scroll_state| start position.
   // Returns SCROLL_STARTED if the layer at the coordinates can be scrolled,
   // SCROLL_ON_MAIN_THREAD if the scroll event should instead be delegated to