[MD History] Disable Clear Browsing Data button for supervised users.

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">
   <template>
     <style include="shared-style">
       :host {
         display: flex;
         height: 100%;
         overflow-x: hidden;
         overflow-y: auto;
         width: var(--side-bar-width);
       }
 
       div.separator {
         background-color: var(--separator-color);
         flex-shrink: 0;
         height: 1px;
         margin: 8px 0;
       }
 
+      a[disabled] {
+        color: var(--paper-grey-400);
+        pointer-events: none;
+      }
+
       #clear-browsing-data {
         justify-content: space-between;
       }
 
       #clear-browsing-data iron-icon {
         -webkit-margin-end: 20px;
         color: var(--paper-grey-400);
         height: 20px;
         margin-bottom: 10px;
         margin-top: 10px;
@@ skipping 59 matching lines @@
         $i18n{historyMenuItem}
         <paper-ripple></paper-ripple>
       </a>
       <a href="/syncedTabs" class="page-item" path="syncedTabs"
           on-click="onItemClick_">
         $i18n{openTabsMenuItem}
         <paper-ripple></paper-ripple>
       </a>
       <div class="separator"></div>
       <a href="chrome://settings/clearBrowserData"
-          on-tap="onClearBrowsingDataTap_" id="clear-browsing-data">
+          on-tap="onClearBrowsingDataTap_" id="clear-browsing-data"
+          disabled$="[[!deletingAllowed_()]]">
         $i18n{clearBrowsingData}
         <iron-icon icon="cr:open-in-new"></iron-icon>
         <paper-ripple id="cbd-ripple"></paper-ripple>
       </a>
       <div id="spacer"></div>
       <div id="footer" hidden="[[!showFooter]]">
         <div class="separator"></div>
         <div id="footer-text">$i18nRaw{sidebarFooter}</div>
       </div>
     </iron-selector>
   </template>
   <script src="chrome://history/side_bar.js"></script>
 </dom-module>