Revert of Remove enable/disable wheel gestures setting.

content/browser/renderer_host/render_widget_host_view_mac.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_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 #define CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_
 
 #import <Cocoa/Cocoa.h>
 #include <IOSurface/IOSurface.h>
 #include <stddef.h>
@@ skipping 311 matching lines @@
 
   bool HasAcceleratedSurface(const gfx::Size& desired_size) override;
   void GetScreenInfo(blink::WebScreenInfo* results) override;
   bool GetScreenColorProfile(std::vector<char>* color_profile) override;
   gfx::Rect GetBoundsInRootWindow() override;
   void LockCompositingSurface() override;
   void UnlockCompositingSurface() override;
 
   bool LockMouse() override;
   void UnlockMouse() override;
+  void WheelEventAck(const blink::WebMouseWheelEvent& event,
+                     InputEventAckState ack_result) override;
   void GestureEventAck(const blink::WebGestureEvent& event,
                        InputEventAckState ack_result) override;
 
   std::unique_ptr<SyntheticGestureTarget> CreateSyntheticGestureTarget()
       override;
 
   uint32_t GetSurfaceIdNamespace() override;
   uint32_t SurfaceIdNamespaceAtPoint(cc::SurfaceHittestDelegate* delegate,
                                      const gfx::Point& point,
                                      gfx::Point* transformed_point) override;
@@ skipping 278 matching lines @@
 
   // Factory used to safely scope delayed calls to ShutdownHost().
   base::WeakPtrFactory<RenderWidgetHostViewMac> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewMac);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_MAC_H_