Implement Wheel Gesture Scrolling on OSX.

ui/events/blink/input_scroll_elasticity_controller.h

 // Copyright 2014 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 UI_EVENTS_BLINK_INPUT_SCROLL_ELASTICITY_CONTROLLER_H_
 #define UI_EVENTS_BLINK_INPUT_SCROLL_ELASTICITY_CONTROLLER_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "cc/input/scroll_elasticity_helper.h"
@@ skipping 40 matching lines @@
   base::WeakPtr<InputScrollElasticityController> GetWeakPtr();
 
   // Update the overscroll state based a wheel event that has been processed.
   // Note that this assumes that all events are coming from a single input
   // device. If the user simultaneously uses multiple input devices, Cocoa may
   // not correctly pass all the gesture begin and end events. In this case,
   // this class may disregard some scrolls that come in at unexpected times.
   void ObserveWheelEventAndResult(
       const blink::WebMouseWheelEvent& wheel_event,
       const cc::InputHandlerScrollResult& scroll_result);
+  // Update the overscroll state based a gesture event that has been processed.
+  // Note that this assumes that all events are coming from a single input
+  // device. If the user simultaneously uses multiple input devices, Cocoa may
+  // not correctly pass all the gesture begin and end events. In this case,
+  // this class may disregard some scrolls that come in at unexpected times.
+  void ObserveGestureEventAndResult(
+      const blink::WebGestureEvent& gesture_event,
+      const cc::InputHandlerScrollResult& scroll_result);
+
   void Animate(base::TimeTicks time);
 
   void ReconcileStretchAndScroll();
 
  private:
   enum State {
     // The initial state, during which the overscroll amount is zero and
     // there are no active or momentum scroll events coming in. This state
     // is briefly returned to between the active and momentum phases of a
     // scroll (if there is no overscroll).
@@ skipping 67 matching lines @@
   // behavior as would happen if the scroll were caused by an active scroll).
   bool momentum_animation_reset_at_next_frame_;
 
   base::WeakPtrFactory<InputScrollElasticityController> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(InputScrollElasticityController);
 };
 
 }  // namespace ui
 
 #endif  // UI_EVENTS_BLINK_INPUT_SCROLL_ELASTICITY_CONTROLLER_H_