Add a WebContentsImpl API to snapshot the accessibility tree.

content/renderer/render_frame_impl.h

 // Copyright 2013 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_FRAME_IMPL_H_
 #define CONTENT_RENDERER_RENDER_FRAME_IMPL_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
@@ skipping 625 matching lines @@
   void OnReload(bool ignore_cache);
   void OnTextSurroundingSelectionRequest(size_t max_length);
   void OnAddStyleSheetByURL(const std::string& url);
   void OnSetupTransitionView(const std::string& markup);
   void OnBeginExitTransition(const std::string& css_selector,
                              bool exit_to_native_app);
   void OnRevertExitTransition();
   void OnHideTransitionElements(const std::string& css_selector);
   void OnShowTransitionElements(const std::string& css_selector);
   void OnSetAccessibilityMode(AccessibilityMode new_mode);
+  void OnSnapshotAccessibilityTree(int callback_id);
   void OnDisownOpener();
   void OnDidUpdateSandboxFlags(SandboxFlags flags);
   void OnTextTrackSettingsChanged(
       const FrameMsg_TextTrackSettings_Params& params);
   void OnPostMessageEvent(const FrameMsg_PostMessage_Params& params);
 #if defined(OS_ANDROID)
   void OnSelectPopupMenuItems(bool canceled,
                               const std::vector<int>& selected_indices);
 #elif defined(OS_MACOSX)
   void OnSelectPopupMenuItem(int selected_index);
@@ skipping 271 matching lines @@
 #endif
 
   base::WeakPtrFactory<RenderFrameImpl> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_FRAME_IMPL_H_