Disable Clear Browsing Data button in History for guest profiles

chrome/browser/resources/md_history/side_bar.html

 <link rel="import" href="chrome://resources/html/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-a11y-keys-behavior/iron-a11y-keys-behavior.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-selector/iron-selector.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-ripple/paper-ripple.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/color.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-styles/typography.html">
 <link rel="import" href="chrome://history/browser_service.html">
 <link rel="import" href="chrome://history/shared_style.html">
 
 <dom-module id="history-side-bar">
@@ skipping 49 matching lines @@
         font-weight: 500;
         min-height: 40px;
         position: relative;
         text-decoration: none;
       }
 
       iron-selector > a.iron-selected {
         color: var(--link-color);
       }
 
+      iron-selector > a[disabled] {
+        opacity: 0.65;
+        pointer-events: none;
+      }
+
       #spacer {
         flex: 1;
       }
 
       #footer {
         color: var(--sidebar-footer-text-color);
         width: var(--side-bar-width);
       }
 
       #footer-text {
@@ skipping 14 matching lines @@
       <a href="/" class="page-item" path="history" on-click="onItemClick_">
         $i18n{historyMenuItem}
         <paper-ripple></paper-ripple>
       </a>
       <a href="/syncedTabs" class="page-item" path="syncedTabs"
           on-click="onItemClick_">
         $i18n{openTabsMenuItem}
         <paper-ripple></paper-ripple>
       </a>
       <div class="separator"></div>
-      <a href="chrome://settings/clearBrowserData"
-          on-tap="onClearBrowsingDataTap_" id="clear-browsing-data">
+      <a id="clear-browsing-data"
+          href="chrome://settings/clearBrowserData"
+          on-tap="onClearBrowsingDataTap_"
+          disabled$="[[guestSession_]]"
+          tabindex$="[[computeClearBrowsingDataTabIndex_(guestSession_)]]">
         $i18n{clearBrowsingData}
         <iron-icon icon="cr:open-in-new"></iron-icon>
         <paper-ripple id="cbd-ripple"></paper-ripple>
       </a>
       <div id="spacer"></div>
       <div id="footer" hidden="[[!showFooter]]">
         <div class="separator"></div>
         <div id="footer-text">$i18nRaw{sidebarFooter}</div>
       </div>
     </iron-selector>
   </template>
   <script src="chrome://history/side_bar.js"></script>
 </dom-module>