Add a WebContentsImpl API to snapshot the accessibility tree.

content/browser/frame_host/render_frame_host_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_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 72 matching lines @@
   // The RenderFrameHost will have a new RenderWidgetHost created and
   // attached to it. This is used when the RenderFrameHost is in a different
   // process from its parent frame.
   CREATE_RF_NEEDS_RENDER_WIDGET_HOST = 1 << 3
 };
 
 class CONTENT_EXPORT RenderFrameHostImpl
     : public RenderFrameHost,
       public BrowserAccessibilityDelegate {
  public:
+  typedef base::Callback<void(const ui::AXTreeUpdate&)>
+      AXTreeSnapshotCallback;
+
   // Keeps track of the state of the RenderFrameHostImpl, particularly with
   // respect to swap out.
   enum RenderFrameHostImplState {
     // The standard state for a RFH handling the communication with an active
     // RenderFrame.
     STATE_DEFAULT = 0,
     // The RFH has not received the SwapOutACK yet, but the new page has
     // committed in a different RFH.  Upon reception of the SwapOutACK, the RFH
     // will either enter STATE_SWAPPED_OUT (if it is a main frame and there are
     // other active frames in its SiteInstance) or it will be deleted.
@@ skipping 255 matching lines @@
                               const base::string16& user_input,
                               bool dialog_was_suppressed);
 
   // Clears any outstanding transition request. This is called when we hear the
   // response or commit.
   void ClearPendingTransitionRequestData();
 
   // Send a message to the renderer process to change the accessibility mode.
   void SetAccessibilityMode(AccessibilityMode AccessibilityMode);
 
+  // Request a one-time snapshot of the accessibility tree without changing
+  // the accessibility mode.
+  void RequestAXTreeSnapshot(AXTreeSnapshotCallback callback);
+
   // Turn on accessibility testing. The given callback will be run
   // every time an accessibility notification is received from the
   // renderer process, and the accessibility tree it sent can be
   // retrieved using GetAXTreeForTesting().
   void SetAccessibilityCallbackForTesting(
       const base::Callback<void(ui::AXEvent, int)>& callback);
 
   // Returns a snapshot of the accessibility tree received from the
   // renderer as of the last time an accessibility notification was
   // received.
@@ skipping 122 matching lines @@
                          const BeginNavigationParams& begin_params,
                          scoped_refptr<ResourceRequestBody> body);
   void OnDispatchLoad();
   void OnAccessibilityEvents(
       const std::vector<AccessibilityHostMsg_EventParams>& params,
       int reset_token);
   void OnAccessibilityLocationChanges(
       const std::vector<AccessibilityHostMsg_LocationChangeParams>& params);
   void OnAccessibilityFindInPageResult(
       const AccessibilityHostMsg_FindInPageResultParams& params);
+  void OnAccessibilitySnapshotResponse(int token,
+                                       const ui::AXTreeUpdate& snapshot);
   void OnToggleFullscreen(bool enter_fullscreen);
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
   void OnShowPopup(const FrameHostMsg_ShowPopup_Params& params);
   void OnHidePopup();
 #endif
 
   // Registers Mojo services that this frame host makes available.
   void RegisterMojoServices();
 
@@ skipping 150 matching lines @@
 
   // This is nonzero if we sent an accessibility reset to the renderer and
   // we're waiting for an IPC containing this reset token (sequentially
   // assigned) and a complete replacement accessibility tree.
   int accessibility_reset_token_;
 
   // A count of the number of times we needed to reset accessibility, so
   // we don't keep trying to reset forever.
   int accessibility_reset_count_;
 
+  // The mapping from request id to corresponding callback for pending
+  // accessibility tree snapshot calls created by RequestAXTreeSnapshot.
+  std::map<int, AXTreeSnapshotCallback> ax_tree_snapshot_callbacks_;
+
   // Callback when an event is received, for testing.
   base::Callback<void(ui::AXEvent, int)> accessibility_testing_callback_;
   // The most recently received accessibility tree - for testing only.
   scoped_ptr<ui::AXTree> ax_tree_for_testing_;
   // Flag to not create a BrowserAccessibilityManager, for testing. If one
   // already exists it will still be used.
   bool no_create_browser_accessibility_manager_for_testing_;
 
   // PlzNavigate: Owns the stream used in navigations to store the body of the
   // response once it has started.
   scoped_ptr<StreamHandle> stream_handle_;
 
   // Context shared for each PermissionService instance created for this RFH.
   scoped_ptr<PermissionServiceContext> permission_service_context_;
 
   // NOTE: This must be the last member.
   base::WeakPtrFactory<RenderFrameHostImpl> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RenderFrameHostImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_RENDER_FRAME_HOST_IMPL_H_