[MD History] Implement grouped history UI.

chrome/browser/resources/md_history/history_list.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-list/iron-list.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-scroll-threshold/iron-scroll-threshold.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/cr_elements/cr_shared_menu/cr_shared_menu.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/constants.html">
 <link rel="import" href="chrome://history/history_item.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
@@ skipping 13 matching lines @@
 
       paper-item {
         -webkit-user-select: none;
         cursor: pointer;
         font: inherit;
       }
 
       paper-item:hover {
         background: #eaeaea;
       }
+
+      history-item {
+        --history-item-padding-side: var(--card-padding-side);
+      }
     </style>
     <div id="no-results" class="centered-message"
-        hidden$="{{hasResults(historyData_.length)}}">
+        hidden$="[[hasResults(historyData_.length)]]">
       {{noResultsMessage_(searchedTerm, querying)}}
     </div>
     <iron-list items="{{historyData_}}" as="item" id="infinite-list"
-        hidden$="{{!hasResults(historyData_.length)}}">
+        hidden$="[[!hasResults(historyData_.length)]]">
       <template>
         <history-item item="[[item]]"
             starred="[[item.starred]]"
             selected="{{item.selected}}"
             is-card-start="[[isCardStart_(item, index, historyData_.length)]]"
             is-card-end="[[isCardEnd_(item, index, historyData_.length)]]"
             has-time-gap="[[needsTimeGap_(item, index, historyData_.length)]]"
             search-term="[[searchedTerm]]"
             number-of-items="[[historyData_.length]]">
         </history-item>
       </template>
     </iron-list>
     <iron-scroll-threshold id="scroll-threshold" scroll-target="infinite-list"
         lower-threshold="500" on-lower-threshold="loadMoreData_">
     </iron-scroll-threshold>
     <cr-shared-menu id="sharedMenu">
       <paper-item id="menuMoreButton" on-tap="onMoreFromSiteTap_">
         $i18n{moreFromSite}
       </paper-item>
       <paper-item id="menuRemoveButton" on-tap="onRemoveFromHistoryTap_">
         $i18n{removeFromHistory}
       </paper-item>
     </cr-shared-menu>
   </template>
   <script src="chrome://history/history_list.js"></script>
 </dom-module>