[MD Extensions] Add logic for opening the extension's home page

chrome/browser/resources/md_extensions/detail_view.html

 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout-classes.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icons/iron-icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-checkbox/paper-checkbox.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable-behavior.html">
 <link rel="import" href="chrome://extensions/animation_helper.html">
 <link rel="import" href="chrome://extensions/item_source.html">
@@ skipping 14 matching lines @@
 
       #top-bar {
         align-items: center;
         color: var(--paper-grey-600);
         display: flex;
         height: 40px;
         margin-bottom: 30px;
         padding: 8px 12px 0;
       }
 
+      a paper-icon-button {
+        color: var(--paper-grey-600);
+      }
+
       #name {
         flex-grow: 1;
       }
 
       .section {
         border-bottom: 1px solid var(--paper-grey-400);
         padding: 12px 20px;
       }
 
       .section:last-child {
@@ skipping 22 matching lines @@
       ul {
         -webkit-padding-start: 20px;
         margin: 0;
       }
     </style>
     <div id="main">
       <div id="top-bar">
         <paper-icon-button id="close-button" icon="arrow-back"
             on-tap="onCloseButtonTap_"></paper-icon-button>
         <span id="name">[[data.name]]</span>
-        <paper-icon-button id="open-in-webstore" icon="open-in-new">
-        </paper-icon-button>
+        <a id="open-homepage" href="[[data.homePage.url]]" tabindex="-1"
+            target="_blank" hidden$="[[!shouldShowHomepageButton_(data.*)]]">
+          <paper-icon-button icon="open-in-new"></paper-icon-button>
+        </a>
         <paper-icon-button id="options" icon="settings"
             on-tap="onOptionsButtonTap_"
             hidden$="[[!shouldShowOptionsButton_(data.*)]]">
         </paper-icon-button>
       </div>
       <div class="section">
         <div class="section-title">$i18n{itemDescriptionLabel}</div>
         <div class="section-content">[[data.description]]</div>
       </div>
       <div class="section">
@@ skipping 63 matching lines @@
       <div class="section">
         <div class="section-title">$i18n{itemSource}</div>
         <div class="section-content">
           [[computeSourceString_(data.*)]]
         </div>
       </div>
     </div>
   </template>
   <script src="chrome://extensions/detail_view.js"></script>
 </dom-module>