Modify ThumbnailStore to make one call to the HistoryBackend using QueryTopUR...

chrome/browser/dom_ui/dom_ui_thumbnail_source.h

Index: chrome/browser/dom_ui/dom_ui_thumbnail_source.h
===================================================================
--- chrome/browser/dom_ui/dom_ui_thumbnail_source.h	(revision 19748)
+++ chrome/browser/dom_ui/dom_ui_thumbnail_source.h	(working copy)
@@ -21,17 +21,11 @@
 class DOMUIThumbnailSource : public ChromeURLDataManager::DataSource {
  public:
   explicit DOMUIThumbnailSource(Profile* profile);
-  virtual ~DOMUIThumbnailSource();
 
   // Called when the network layer has requested a resource underneath
   // the path we registered.
   virtual void StartDataRequest(const std::string& path, int request_id);
 
-  // Used only when chromium is invoked with the --thumbnail-store switch.
-  // If StartDataRequest does not return thumbnail data synchronously, this
-  // method will be invoked when the thumbnail data becomes available.
-  virtual void ReturnData(int request_id, scoped_refptr<RefCountedBytes> data);
-
   virtual std::string GetMimeType(const std::string&) const {
     // We need to explicitly return a mime type, otherwise if the user tries to
     // drag the image they get no extension.
@@ -46,9 +40,6 @@
   Profile* profile_;
   CancelableRequestConsumerT<int, 0> cancelable_consumer_;
 
-  // A set of outstanding request_id's. These are canceled on destruction.
-  std::set<int> pending_requests_;
-
   // The ThumbnailStore from which thumbnails are requested.
   scoped_refptr<ThumbnailStore> store_;