Add ToString to AXTreeUpdate.

content/renderer/accessibility/renderer_accessibility_complete.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_complete.h"
 
 #include <queue>
 
 #include "base/bind.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 189 matching lines @@
     // of read-only queries at once.
     obj.startCachingComputedObjectAttributesUntilTreeMutates();
 
     AccessibilityHostMsg_EventParams event_msg;
     event_msg.event_type = event.event_type;
     event_msg.id = event.id;
     serializer_.SerializeChanges(obj, &event_msg.update);
     event_msgs.push_back(event_msg);
 
 #ifndef NDEBUG
-    ui::AXTree tree;
-    tree.Unserialize(event_msg.update);
     VLOG(0) << "Accessibility update: \n"
             << "routing id=" << routing_id()
             << " event="
             << AccessibilityEventToString(event.event_type)
-            << "\n" << tree.ToString();
+            << "\n" << event_msg.update.ToString();
 #endif
   }
 
   Send(new AccessibilityHostMsg_Events(routing_id(), event_msgs));
 
   SendLocationChanges();
 }
 
 void RendererAccessibilityComplete::SendLocationChanges() {
   std::vector<AccessibilityHostMsg_LocationChangeParams> messages;
@@ skipping 155 matching lines @@
     render_view()->GetWebView()->clearFocusedElement();
   else
     obj.setFocused(true);
 }
 
 void RendererAccessibilityComplete::OnFatalError() {
   CHECK(false) << "Invalid accessibility tree.";
 }
 
 }  // namespace content