Implement Wheel Gesture Scrolling on OSX.

content/renderer/render_widget.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_RENDERER_RENDER_WIDGET_H_
 #define CONTENT_RENDERER_RENDER_WIDGET_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 195 matching lines @@
   void RequestScheduleAnimation() override;
   void UpdateVisualState() override;
   void WillBeginCompositorFrame() override;
 
   // RenderWidgetInputHandlerDelegate
   void FocusChangeComplete() override;
   bool HasTouchEventHandlersAt(const gfx::Point& point) const override;
   void ObserveWheelEventAndResult(const blink::WebMouseWheelEvent& wheel_event,
                                   const gfx::Vector2dF& wheel_unused_delta,
                                   bool event_processed) override;
+  void ObserveGestureEventAndResult(const blink::WebGestureEvent& gesture_event,
+                                    const gfx::Vector2dF& unused_delta,
+                                    bool event_processed) override;
+
   void OnDidHandleKeyEvent() override;
   void OnDidOverscroll(const DidOverscrollParams& params) override;
   void OnInputEventAck(scoped_ptr<InputEventAck> input_event_ack) override;
   void NonBlockingInputEventHandled(
       blink::WebInputEvent::Type handled_type) override;
   void SetInputHandler(RenderWidgetInputHandler* input_handler) override;
   void UpdateTextInputState(ShowIme show_ime,
                             ChangeSource change_source) override;
   bool WillHandleGestureEvent(const blink::WebGestureEvent& event) override;
   bool WillHandleMouseEvent(const blink::WebMouseEvent& event) override;
@@ skipping 557 matching lines @@
  private:
   // When emulated, this returns original device scale factor.
   float GetOriginalDeviceScaleFactor() const;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidget);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_WIDGET_H_