Implement Wheel Gesture Scrolling on OSX.

content/renderer/input/input_handler_manager.h

Index: content/renderer/input/input_handler_manager.h
diff --git a/content/renderer/input/input_handler_manager.h b/content/renderer/input/input_handler_manager.h
index c8bfb75262e6d3be82b6afda9e59568086c39140..96d42cc046d45f5bfaff72cde1173d52c2379110 100644
--- a/content/renderer/input/input_handler_manager.h
+++ b/content/renderer/input/input_handler_manager.h
@@ -61,6 +61,11 @@ class InputHandlerManager {
       const blink::WebMouseWheelEvent& wheel_event,
       const cc::InputHandlerScrollResult& scroll_result);
 
+  void ObserveGestureEventAndResultOnMainThread(
+      int routing_id,
+      const blink::WebGestureEvent& gesture_event,
+      const cc::InputHandlerScrollResult& scroll_result);
+
   void NonBlockingInputEventHandledOnMainThread(int routing_id,
                                                 blink::WebInputEvent::Type);
 
@@ -96,6 +101,11 @@ class InputHandlerManager {
       const blink::WebMouseWheelEvent& wheel_event,
       const cc::InputHandlerScrollResult& scroll_result);
 
+  void ObserveGestureEventAndResultOnCompositorThread(
+      int routing_id,
+      const blink::WebGestureEvent& gesture_event,
+      const cc::InputHandlerScrollResult& scroll_result);
+
   void NonBlockingInputEventHandledOnCompositorThread(
       int routing_id,
       blink::WebInputEvent::Type);