Add a WebContentsImpl API to snapshot the accessibility tree.

content/renderer/accessibility/renderer_accessibility.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_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_
 #define CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_
 
 #include <vector>
 
 #include "base/containers/hash_tables.h"
@@ skipping 28 matching lines @@
 // accessible objects that can be used to respond to accessibility requests
 // from other processes.
 //
 // This class implements complete accessibility support for assistive
 // technology. It turns on Blink's accessibility code and sends a serialized
 // representation of that tree whenever it changes. It also handles requests
 // from the browser to perform accessibility actions on nodes in the tree
 // (e.g., change focus, or click on a button).
 class CONTENT_EXPORT RendererAccessibility : public RenderFrameObserver {
  public:
+  // Request a one-time snapshot of the accessibility tree without
+  // enabling accessibility if it wasn't already enabled.
+  static void SnapshotAccessibilityTree(RenderFrameImpl* render_frame,
+                                        ui::AXTreeUpdate* response);
+
   explicit RendererAccessibility(RenderFrameImpl* render_frame);
   ~RendererAccessibility() override;
 
   // RenderFrameObserver implementation.
   bool OnMessageReceived(const IPC::Message& message) override;
 
   // Called when an accessibility notification occurs in Blink.
   void HandleWebAccessibilityEvent(const blink::WebAXObject& obj,
                                    blink::WebAXEvent event);
 
@@ skipping 72 matching lines @@
 
   // So we can queue up tasks to be executed later.
   base::WeakPtrFactory<RendererAccessibility> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RendererAccessibility);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_ACCESSIBILITY_RENDERER_ACCESSIBILITY_H_