MD Downloads: finally use allow-outside-scroll and drop the pushScrollLock hack

chrome/browser/resources/md_downloads/toolbar.html

 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/html/util.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-menu/paper-menu.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-menu-button/paper-menu-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_search_field/cr_search_field.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 
 <dom-module id="downloads-toolbar">
   <template>
     <div id="title">
       <h1>$i18n{title}</h1>
     </div>
     <div id="actions">
       <paper-button class="clear-all" on-tap="onClearAllTap_">
         $i18n{clearAll}
       </paper-button>
       <paper-button on-tap="onOpenDownloadsFolderTap_">
         $i18n{openDownloadsFolder}
       </paper-button>
     </div>
     <div id="search">
       <cr-search-field id="search-input" label="$i18n{search}"
           clear-label="$i18n{clearSearch}"
           on-search-changed="onSearchChanged_"></cr-search-field>
-      <paper-menu-button id="more" horizontal-align="[[overflowAlign_]]">
+      <paper-menu-button id="more" horizontal-align="[[overflowAlign_]]"
+          allow-outside-scroll>
         <paper-icon-button icon="cr:more-vert" title="$i18n{moreActions}"
              class="dropdown-trigger"></paper-icon-button>
         <paper-menu class="dropdown-content">
           <paper-item class="clear-all" on-tap="onClearAllTap_"
               on-blur="onItemBlur_">
             $i18n{clearAll}
           </paper-item>
           <paper-item on-tap="onOpenDownloadsFolderTap_" on-blur="onItemBlur_">
             $i18n{openDownloadsFolder}
           </paper-item>
         </paper-menu>
       </paper-menu-button>
     </div>
   </template>
   <link rel="import" type="css" href="chrome://downloads/shared_style.css">
   <link rel="import" type="css" href="chrome://downloads/toolbar.css">
   <script src="chrome://downloads/toolbar.js"></script>
 </dom-module>