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

chrome/browser/resources/md_history/history_item.html

Index: chrome/browser/resources/md_history/history_item.html
diff --git a/chrome/browser/resources/md_history/history_item.html b/chrome/browser/resources/md_history/history_item.html
index 26bee11f15b8671a5859d7ce518c5184c44ebb04..0a11c48ff7f9424c531e8a92bb87c9328fcdfed8 100644
--- a/chrome/browser/resources/md_history/history_item.html
+++ b/chrome/browser/resources/md_history/history_item.html
@@ -83,7 +83,7 @@
     </style>
     <div id="main-container">
       <paper-checkbox id="checkbox" on-tap="onCheckboxSelected_"
-          checked="{{selected}}">
+          checked="{{selected}}" disabled="{{selectionNotAllowed_()}}">

[tsergeant, 2016/02/01 22:47:53]

Nit: probably use one-way binding here

[hsampson, 2016/02/02 00:45:10]

Done.

       </paper-checkbox>
       <span id="time">{{timeAccessed_}}</span>
       <div id="website-icon"></div>