Use copies of canned browsing data helpers to populate the cookies tree model.

chrome/browser/browsing_data_indexed_db_helper.h

Index: chrome/browser/browsing_data_indexed_db_helper.h
diff --git a/chrome/browser/browsing_data_indexed_db_helper.h b/chrome/browser/browsing_data_indexed_db_helper.h
index e0f25b63ae1229b4b01df71ab740da3f785b64f2..fa49d583b76a7fe0a1d6b50faeedb006d2b631be 100644
--- a/chrome/browser/browsing_data_indexed_db_helper.h
+++ b/chrome/browser/browsing_data_indexed_db_helper.h
@@ -85,6 +85,11 @@ class CannedBrowsingDataIndexedDBHelper
  public:
   explicit CannedBrowsingDataIndexedDBHelper(Profile* profile);
 
+  // Return a copy of the IndexedDB helper. Only one consumer can use the
+  // StartFetching method at a time, so we need to create a copy of the helper
+  // everytime we instantiate a cookies tree model for it.
+  CannedBrowsingDataIndexedDBHelper* Clone();
+
   // Add a indexed database to the set of canned indexed databases that is
   // returned by this helper.
   void AddIndexedDB(const GURL& origin,