fix dnd in bookmark manager

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

 // Copyright (c) 2012 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.
 
 const BookmarkList = bmm.BookmarkList;
 const BookmarkTree = bmm.BookmarkTree;
 const ListItem = cr.ui.ListItem;
 const TreeItem = cr.ui.TreeItem;
 const LinkKind = cr.LinkKind;
 const Command = cr.ui.Command;
@@ skipping 748 matching lines @@
       else if (dropPos == 'below')
         index = relatedIndex + 1;
 
       selectItemsAfterUserAction(selectTarget, selectedTreeId);
 
       if (index != undefined && index != -1)
         chrome.experimental.bookmarkManager.drop(parentId, index);
       else
         chrome.experimental.bookmarkManager.drop(parentId);
 
+      e.preventDefault();
+
       // TODO(arv): Select the newly dropped items.
     }
     this.dropDestination = null;
     this.hideDropOverlay_();
   },
 
   clearDragData: function() {
     this.dragData = null;
   },
 
@@ skipping 766 matching lines @@
   document.addEventListener('copy', handle('copy-command'));
   document.addEventListener('cut', handle('cut-command'));
 
   var pasteHandler = handle('paste-command');
   document.addEventListener('paste', function(e) {
     // Paste is a bit special since we need to do an async call to see if we can
     // paste because the paste command might not be up to date.
     updatePasteCommand(pasteHandler);
   });
 })();