[MD History] Add grouped history toolbar.

chrome/browser/resources/md_history/app.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-pages/iron-pages.html">
 <link rel="import" href="chrome://history/history_list.html">
 <link rel="import" href="chrome://history/history_toolbar.html">
 <link rel="import" href="chrome://history/synced_device_manager.html">
 <link rel="import" href="chrome://history/side_bar.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-app">
   <!-- TODO(calamity): work around this deprecated import style -->
   <link rel="import" type="css" href="chrome://resources/css/md_colors.css">
   <template>
     <style include="shared-style">
       :host {
         display: flex;
         flex-direction: column;
         min-width: 800px;
       }
 
       #main-container {
         display: flex;
         flex: 1 0 0;
         overflow: hidden;
       }
 
-      #toolbar {
-        flex: 0 0 56px;
-      }
-
       history-list,
       #history-synced-device-manager {
         flex: 1 0 0;
       }
 
       #content {
         display: flex;
         flex: 1 0 0;
       }
 
       history-toolbar {
         background: var(--md-toolbar-color);
       }
     </style>
-    <history-toolbar class="paper-header" id="toolbar"></history-toolbar>
+    <history-toolbar id="toolbar"></history-toolbar>
 
     <div id="main-container">
       <history-side-bar id="history-side-bar" selected-page="{{selectedPage}}">
       </history-side-bar>
       <iron-pages id="content" attr-for-selected="id"
           selected="{{selectedPage}}">
         <history-list id="history-list"></history-list>
         <history-synced-device-manager id="history-synced-device-manager">
         </history-synced-device-manager>
       </iron-pages>
     </div>
   </template>
   <script src="chrome://history/app.js"></script>
 </dom-module>