fix dnd in bookmark manager

preventDefault in handleDrop, as suggested by arv

BUG=122850
TEST=manual

Review URL: https://chromiumcodereview.appspot.com/10065034

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132203 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/bookmark_manager/js/main.js

@@ -766,6 +766,8 @@ var dnd = {
       else
         chrome.experimental.bookmarkManager.drop(parentId);
 
+      e.preventDefault();
+
       // TODO(arv): Select the newly dropped items.
     }
     this.dropDestination = null;