Add a WebContentsImpl API to snapshot the accessibility tree.

content/renderer/accessibility/renderer_accessibility.cc

 // 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.
 
 #include "content/renderer/accessibility/renderer_accessibility.h"
 
 #include <queue>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/utf_string_conversions.h"
 #include "content/renderer/accessibility/blink_ax_enum_conversion.h"
 #include "content/renderer/render_frame_impl.h"
 #include "content/renderer/render_view_impl.h"
 #include "third_party/WebKit/public/web/WebAXObject.h"
 #include "third_party/WebKit/public/web/WebDocument.h"
 #include "third_party/WebKit/public/web/WebInputElement.h"
 #include "third_party/WebKit/public/web/WebLocalFrame.h"
 #include "third_party/WebKit/public/web/WebSettings.h"
 #include "third_party/WebKit/public/web/WebView.h"
 
 using blink::WebAXObject;
 using blink::WebDocument;
 using blink::WebLocalFrame;
 using blink::WebNode;
 using blink::WebPoint;
 using blink::WebRect;
+using blink::WebScopedAXContext;
 using blink::WebSettings;
 using blink::WebView;
 
 namespace content {
 
+// static
+void RendererAccessibility::SnapshotAccessibilityTree(
+    RenderFrameImpl* render_frame,
+    ui::AXTreeUpdate* response) {
+  DCHECK(render_frame);
+  DCHECK(response);
+  if (!render_frame->GetWebFrame())
+    return;
+
+  WebDocument document = render_frame->GetWebFrame()->document();
+  WebScopedAXContext context(document);
+  BlinkAXTreeSource tree_source(render_frame);
+  tree_source.SetRoot(context.root());
+  ui::AXTreeSerializer<blink::WebAXObject> serializer(&tree_source);
+  serializer.SerializeChanges(context.root(), response);
+}
+
 RendererAccessibility::RendererAccessibility(RenderFrameImpl* render_frame)
     : RenderFrameObserver(render_frame),
       render_frame_(render_frame),
       tree_source_(render_frame),
       serializer_(&tree_source_),
       last_scroll_offset_(gfx::Size()),
       ack_pending_(false),
       reset_token_(0),
       weak_factory_(this) {
   WebView* web_view = render_frame_->GetRenderView()->GetWebView();
@@ skipping 443 matching lines @@
     LOG(WARNING) << "SetTextSelection on invalid object id " << acc_obj_id;
 #endif
     return;
   }
 
   obj.setValue(value);
   HandleAXEvent(obj, ui::AX_EVENT_VALUE_CHANGED);
 }
 
 }  // namespace content