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

third_party/WebKit/Source/web/WebAXObject.cpp

Index: third_party/WebKit/Source/web/WebAXObject.cpp
diff --git a/third_party/WebKit/Source/web/WebAXObject.cpp b/third_party/WebKit/Source/web/WebAXObject.cpp
index c0e2205b9ce8bbdf3a20df8119cd9d89aff7919b..9b5e11b57558aa3a1556f7f0f60c15fcaccf21a8 100644
--- a/third_party/WebKit/Source/web/WebAXObject.cpp
+++ b/third_party/WebKit/Source/web/WebAXObject.cpp
@@ -608,6 +608,13 @@ bool WebAXObject::canvasHasFallbackContent() const {
   return m_private->canvasHasFallbackContent();
 }
 
+WebString WebAXObject::imageDataUrl(const WebSize& maxSize) const {
+  if (isDetached())
+    return WebString();
+
+  return m_private->imageDataUrl(maxSize);
+}
+
 WebAXInvalidState WebAXObject::invalidState() const {
   if (isDetached())
     return WebAXInvalidStateUndefined;