MD History: Delete button in the toolbar allows deletion of multiple history-items.

chrome/browser/resources/md_history/history_item.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.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-icons/iron-icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.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">
 
 <dom-module id="history-item">
   <template>
     <style>
@@ skipping 64 matching lines @@
       #bookmark {
         -webkit-margin-end: 10px;
         -webkit-margin-start: 20px;
         color: #48f;
         min-width: 16px;
         visibility: hidden;
       }
     </style>
     <div id="main-container">
       <paper-checkbox id="checkbox" on-tap="checkboxSelected"
-          checked="{{selected}}">
+          checked="{{selected}}" disabled="{{selectionAllowed_()}}">

[tsergeant, 2016/01/25 01:43:14]

I'm not convinced about this pattern...but I don't have any better ideas for
now.

(Mainly since this will only ever be called once, so you're relying on
loadTimeData being ready by that point).

[hsampson, 2016/01/25 04:15:42]

Acknowledged.

       </paper-checkbox>
       <span id="time">{{timeAccessed}}</span>
       <div id="website-icon"></div>
       <a href="{{websiteUrl}}" id="title">{{websiteTitle}}</a>
       <span id="domain">{{websiteDomain}}</span>
       <iron-icon icon="star" id="bookmark"></iron-icon>
       <paper-icon-button icon="more-vert" id="menu-button" on-tap="openMenu">
       </paper-icon-button>
     </div>
   </template>
   <script src="chrome://history/history_item.js"></script>
 
 </dom-module>