MD History: Convert synced device collapse icon to a button

chrome/browser/resources/md_history/synced_device_card.html

 <link rel="import" href="chrome://resources/cr_elements/icons.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
-<link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/shadow.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-collapse/iron-collapse.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.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/paper-icon-button/paper-icon-button-light.html">
 <link rel="import" href="chrome://resources/html/icon.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/constants.html">
 <link rel="import" href="chrome://history/searched_label.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-synced-device-card">
   <template>
     <style include="shared-style">
       :host {
@@ skipping 18 matching lines @@
       #open-tabs {
         -webkit-margin-start: 20px;
         color: rgb(102, 136, 238);
         cursor: pointer;
       }
 
       #last-update-time {
         color: var(--secondary-text-color);
       }
 
-      #dropdown-indicator {
-        -webkit-margin-end: 12px;
-        color: var(--secondary-text-color);
-        height: 20px;
-        width: 20px;
+      .card-title .icon-button {
+        -webkit-margin-end: 4px;
       }
 
       #collapse {
         border-bottom: 1px solid var(--card-border-color);
         overflow: hidden;
       }
 
       #history-item-container {
         background: #fff;
         border: 1px solid var(--card-border-color);
@@ skipping 13 matching lines @@
         width: 80%;
       }
     </style>
     <div id="history-item-container">
       <div class="card-title" id="card-heading" aria-expanded$="[[cardOpen_]]"
           aria-controls="collapse" on-tap="toggleTabCard">
         <div>
           [[device]]
           <span id="last-update-time">[[lastUpdateTime]]</span>
         </div>
-        <iron-icon icon="cr:expand-less" id="dropdown-indicator"></iron-icon>
+        <button is="paper-icon-button-light" class="icon-button"
+            title$="[[getCollapseTitle_(cardOpen_)]]">
+          <iron-icon icon="cr:expand-less" id="dropdown-indicator">
+          </iron-icon>
+        </button>
       </div>
 
       <iron-collapse opened="{{cardOpen_}}" id="collapse">
         <div id="tab-item-list">
           <template is="dom-repeat" items="[[tabs]]" as="tab" id="tab-list">
             <div id="item-container">
               <div id="icon" class="website-icon"></div>
               <a href="[[tab.url]]" class="website-title" title="[[tab.title]]"
                   on-tap="openTab_">
                 <history-searched-label title="[[tab.title]]"
                     search-term="[[searchTerm]]"></history-searched-label>
               </a>
             </div>
             <div id="window-separator"
                 hidden$="[[!isWindowSeparatorIndex_(index, separatorIndexes)]]">
             </div>
           </template>
           <div class="item-container">
             <p on-tap="openAllTabs_" id="open-tabs">$i18n{openAll}</p>
           </div>
         </div>
       </iron-collapse>
     </div>
   </template>
   <script src="chrome://history/synced_device_card.js"></script>
 </dom-module>