MD Bookmarks: Add right-click context menu to sidebar folders

chrome/browser/resources/md_bookmarks/folder_node.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://bookmarks/actions.html">
 <link rel="import" href="chrome://bookmarks/command_manager.html">
 <link rel="import" href="chrome://bookmarks/icons.html">
 <link rel="import" href="chrome://bookmarks/mouse_focus_behavior.html">
 <link rel="import" href="chrome://bookmarks/shared_style.html">
@@ skipping 66 matching lines @@
 
       [no-children] {
         -webkit-padding-start: 52px; /* The width of the arrow and its margin */
       }
     </style>
 
     <div id="container"
         class="v-centered"
         draggable="true"
         on-tap="selectFolder_"
+        on-contextmenu="onContextMenu_"
         tabindex$="[[getTabIndex_(isSelectedFolder_)]]"
         hidden="[[isRootFolder_(depth)]]">
       <template is="dom-if" if="[[hasChildFolder_(item_.children)]]">
         <button is="paper-icon-button-light" id="arrow"
             on-tap="toggleFolder_" on-mousedown="preventDefault_" tabindex="-1">
           <iron-icon icon="cr:arrow-drop-down" is-open$="[[!isClosed_]]">
           </iron-icon>
         </button>
       </template>
       <div id="folder-label" class="v-centered">
         <iron-icon icon="[[getFolderIcon_(isSelectedFolder_)]]"
             no-children$="[[!hasChildFolder_(item_.children)]]">
         </iron-icon>
         <div class="menu-label">[[item_.title]]</div>
       </div>
     </div>
     <div id="descendants" hidden$="[[isClosed_]]">
       <template is="dom-repeat"
           items="[[item_.children]]"
           as="child"
           filter="isFolder_">
         <bookmarks-folder-node item-id="[[child]]"
             depth="[[getChildDepth_(depth)]]">
         </bookmarks-folder-node>
       </template>
     </div>
   </template>
   <script src="chrome://bookmarks/folder_node.js"></script>
 </dom-module>