MD History: Use computed functions for card borders and time gaps

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/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/constants.html">
 <link rel="import" href="chrome://history/history_item.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-list">
   <template>
@@ skipping 23 matching lines @@
         hidden$="{{hasResults(historyData.length)}}">
       {{noResultsMessage_(searchTerm, loading_)}}
     </div>
     <iron-list items="{{historyData}}" as="item" id="infinite-list"
         on-scroll="scrollHandler_"
         hidden$="{{!hasResults(historyData.length)}}">
       <template>
         <history-item item="[[item]]"
             starred="[[item.starred]]"
             selected="{{item.selected}}"
-            is-card-start="[[item.isFirstItem]]"
-            is-card-end="[[item.isLastItem]]"
+            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="[[searchTerm]]"
             number-of-items="[[historyData.length]]">
         </history-item>
       </template>
     </iron-list>
     <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>