MD History: Lazily load element files which are not needed for first paint

chrome/browser/resources/md_history/shared_style.html

 <link rel="import" href="chrome://history/shared_vars.html">
 
 <dom-module id="shared-style">
   <template>
     <style>
       [hidden] {
         display: none !important;
       }
 
       .card-title {
@@ skipping 40 matching lines @@
 
       .website-title {
         color: var(--primary-text-color);
         overflow: hidden;
         text-decoration: none;
         text-overflow: ellipsis;
         white-space: nowrap;
       }
 
       button.icon-button {
+        background: none;
+        border: none;
         height: 36px;
+        outline: none;
         width: 36px;
       }
 
       button.icon-button iron-icon {
         color: var(--secondary-text-color);
         height: 20px;
         width: 20px;
       }
 
       button.more-vert-button {
         height: 36px;
         padding: 6px;
         width: 36px;
       }
 
       button.more-vert-button div {
         border: 2px solid var(--secondary-text-color);
         border-radius: 2px;
         margin: 1px 10px;
         pointer-events: none;
         transform: scale(0.8);
       }
     </style>
   </template>
 </dom-module>