Implement Wheel Gesture Scrolling on OSX.

content/renderer/input/render_widget_input_handler_delegate.h

Index: content/renderer/input/render_widget_input_handler_delegate.h
diff --git a/content/renderer/input/render_widget_input_handler_delegate.h b/content/renderer/input/render_widget_input_handler_delegate.h
index 7a7f54461815f04fd1136b914e080683ea1e427b..f4bbe1bbc1eae540b7e1072c5dc12e3001efe415 100644
--- a/content/renderer/input/render_widget_input_handler_delegate.h
+++ b/content/renderer/input/render_widget_input_handler_delegate.h
@@ -49,6 +49,11 @@ class CONTENT_EXPORT RenderWidgetInputHandlerDelegate {
       const gfx::Vector2dF& wheel_unused_delta,
       bool event_processed) = 0;
 
+  virtual void ObserveGestureEventAndResult(
+      const blink::WebGestureEvent& gesture_event,
+      const gfx::Vector2dF& unused_delta,
+      bool event_processed) = 0;
+
   // Notifies that a key event was just handled.
   virtual void OnDidHandleKeyEvent() = 0;