[MD Bookmarks] Add a drag and drop indicator to bookmarks.

chrome/browser/resources/md_bookmarks/item.js

Index: chrome/browser/resources/md_bookmarks/item.js
diff --git a/chrome/browser/resources/md_bookmarks/item.js b/chrome/browser/resources/md_bookmarks/item.js
index e7590a76c4b6699be3540e439f660453c95122f5..362df7ee9666b0fcee71f2a2b71a54cb06d6ba2e 100644
--- a/chrome/browser/resources/md_bookmarks/item.js
+++ b/chrome/browser/resources/md_bookmarks/item.js
@@ -40,6 +40,7 @@ Polymer({
     'dblclick': 'onDblClick_',
   },
 
+  /** @override */
   attached: function() {
     this.watch('item_', function(store) {
       return store.nodes[this.itemId];
@@ -51,6 +52,11 @@ Polymer({
     this.updateFromStore();
   },
 
+  /** @return {BookmarksItemElement} */
+  getDropTarget: function() {
+    return this;
+  },
+
   /**
    * @param {Event} e
    * @private