MD History: Improve styling of grouped history toolbar during page load

chrome/browser/resources/md_history/history_toolbar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_lazy_render/cr_lazy_render.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_toolbar/cr_toolbar.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/icons.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <!-- Lazy loaded: iron-dropdown, paper-button, paper-icon-button-light,
@@ skipping 93 matching lines @@
         flex: 1;
       }
 
       #cancel-icon-button {
         -webkit-margin-end: 24px;
         -webkit-margin-start: 2px;
       }
 
       /* Grouped toolbar. */
 
+      paper-tabs:unresolved {
+        visibility: hidden;
+      }
+
       paper-tabs {
         /* TODO(tsergeant): Align tabs with cards. */
         --paper-tabs: {
           font-size: inherit;
         };
         --paper-tabs-selection-bar-color: #fff;
         -webkit-margin-start: 32px;
         height: calc(var(--toolbar-grouped-height) - var(--toolbar-height));
         min-width: 300px;
       }
@@ skipping 129 matching lines @@
               on-click="onNextTap_"
               disabled="[[isToday_(groupedOffset)]]">
             <iron-icon icon="cr:chevron-right"></iron-icon>
           </button>
         </div>
       </div>
     </template>
   </template>
   <script src="chrome://history/history_toolbar.js"></script>
 </dom-module>