mac: Only let two-finger-scrolling trigger history if web doesn't swallow gesture

chrome/browser/renderer_host/render_widget_host_view_gtk.h

 // Copyright (c) 2011 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 CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_GTK_H_
 #define CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_GTK_H_
 #pragma once
 
 #include <gdk/gdk.h>
 
@@ skipping 80 matching lines @@
                                 const ui::Range& range,
                                 const gfx::Point& start,
                                 const gfx::Point& end) OVERRIDE;
   virtual void ShowingContextMenu(bool showing) OVERRIDE;
   virtual BackingStore* AllocBackingStore(const gfx::Size& size) OVERRIDE;
   virtual void SetBackground(const SkBitmap& background) OVERRIDE;
   virtual void CreatePluginContainer(gfx::PluginWindowHandle id) OVERRIDE;
   virtual void DestroyPluginContainer(gfx::PluginWindowHandle id) OVERRIDE;
   virtual void SetVisuallyDeemphasized(const SkColor* color,
                                        bool animate) OVERRIDE;
+  virtual void UnhandledWheelEvent(
+      const WebKit::WebMouseWheelEvent& event) OVERRIDE;
+  virtual void SetHasHorizontalScrollbar(
+      bool has_horizontal_scrollbar) OVERRIDE;
+  virtual void SetScrollOffsetPinning(
+      bool is_pinned_to_left, bool is_pinned_to_right) OVERRIDE;
   virtual void AcceleratedCompositingActivated(bool activated) OVERRIDE;
   virtual gfx::PluginWindowHandle GetCompositingSurface() OVERRIDE;
 
   // ui::AnimationDelegate implementation.
   virtual void AnimationEnded(const ui::Animation* animation) OVERRIDE;
   virtual void AnimationProgressed(const ui::Animation* animation) OVERRIDE;
   virtual void AnimationCanceled(const ui::Animation* animation) OVERRIDE;
 
   gfx::NativeView native_view() const { return view_.get(); }
 
@@ skipping 151 matching lines @@
   // menus and drags.
   GdkEventButton* last_mouse_down_;
 
 #if defined(OS_CHROMEOS)
   // Custimized tooltip window.
   scoped_ptr<views::TooltipWindowGtk> tooltip_window_;
 #endif  // defined(OS_CHROMEOS)
 };
 
 #endif  // CHROME_BROWSER_RENDERER_HOST_RENDER_WIDGET_HOST_VIEW_GTK_H_