MouseWheelEventQueue should respect ScrollBegin/End state from RenderWidgetHost.

content/browser/renderer_host/input/mock_input_router_client.h

Index: content/browser/renderer_host/input/mock_input_router_client.h
diff --git a/content/browser/renderer_host/input/mock_input_router_client.h b/content/browser/renderer_host/input/mock_input_router_client.h
index 463d7f694f44231c55dde8109cd836f33062760e..9be5454edd0f9e9e2446e2111ebd91ef03c0935a 100644
--- a/content/browser/renderer_host/input/mock_input_router_client.h
+++ b/content/browser/renderer_host/input/mock_input_router_client.h
@@ -36,6 +36,7 @@ class MockInputRouterClient : public InputRouterClient {
   void ForwardGestureEventWithLatencyInfo(
       const blink::WebGestureEvent& gesture_event,
       const ui::LatencyInfo& latency_info) override;
+  bool IsInGestureScroll(blink::WebGestureDevice device) const override;
 
   bool GetAndResetFilterEventCalled();
   size_t GetAndResetDidFlushCount();
@@ -63,6 +64,7 @@ class MockInputRouterClient : public InputRouterClient {
   InputRouter* input_router_;
   int in_flight_event_count_;
   bool has_touch_handler_;
+  bool is_in_gesture_scroll_;
 
   InputEventAckState filter_state_;