Implement "Save image as" for canvas (chromium side).

content/renderer/render_view_impl.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_VIEW_IMPL_H_
 #define CONTENT_RENDERER_RENDER_VIEW_IMPL_H_
 
 #include <deque>
 #include <map>
 #include <set>
@@ skipping 738 matching lines @@
   void OnMoveCaret(const gfx::Point& point);
   void OnScrollFocusedEditableNodeIntoRect(const gfx::Rect& rect);
   void OnSetEditCommandsForNextKeyEvent(const EditCommands& edit_commands);
   void OnAllowBindings(int enabled_bindings_flags);
   void OnAllowScriptToClose(bool script_can_close);
   void OnCancelDownload(int32 download_id);
   void OnClearFocusedElement();
   void OnClosePage();
   void OnShowContextMenu(const gfx::Point& location);
   void OnCopyImageAt(int x, int y);
+  void OnSaveImageAt(int x, int y);
   void OnSetName(const std::string& name);
   void OnDeterminePageLanguage();
   void OnDisableScrollbarsForSmallWindows(
       const gfx::Size& disable_scrollbars_size_limit);
   void OnDragSourceEnded(const gfx::Point& client_point,
                          const gfx::Point& screen_point,
                          blink::WebDragOperation drag_operation);
   void OnDragSourceSystemDragEnded();
   void OnDragTargetDrop(const gfx::Point& client_pt,
                         const gfx::Point& screen_pt,
@@ skipping 540 matching lines @@
   // use the Observer interface to filter IPC messages and receive frame change
   // notifications.
   // ---------------------------------------------------------------------------
 
   DISALLOW_COPY_AND_ASSIGN(RenderViewImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_VIEW_IMPL_H_