Add support for retrieving image thumbnails as part of the accessibility tree.

ui/accessibility/ax_node_data.cc

 // 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.
 
 #include "ui/accessibility/ax_node_data.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <set>
@@ skipping 598 matching lines @@
         break;
       case AX_ATTR_DISPLAY:
         result += " display=" + value;
         break;
       case AX_ATTR_FONT_FAMILY:
         result += " font-family=" + value;
         break;
       case AX_ATTR_HTML_TAG:
         result += " html_tag=" + value;
         break;
+      case AX_ATTR_IMAGE_DATA_URL:
+        result += " image_data_url=(" +
+            IntToString(static_cast<int>(value.size())) + " bytes)";
+        break;
       case AX_ATTR_LANGUAGE:
         result += " language=" + value;
         break;
       case AX_ATTR_LIVE_RELEVANT:
         result += " relevant=" + value;
         break;
       case AX_ATTR_LIVE_STATUS:
         result += " live=" + value;
         break;
       case AX_ATTR_CONTAINER_LIVE_RELEVANT:
@@ skipping 152 matching lines @@
     }
   }
 
   if (!child_ids.empty())
     result += " child_ids=" + IntVectorToString(child_ids);
 
   return result;
 }
 
 }  // namespace ui