MD History: Add shortcuts for 'Delete' and 'Backspace' to delete selected items

chrome/browser/resources/md_history/history_list.js

Index: chrome/browser/resources/md_history/history_list.js
diff --git a/chrome/browser/resources/md_history/history_list.js b/chrome/browser/resources/md_history/history_list.js
index ba358120f6b4f93984e925bb05bad7a508f37f7f..dc1f42acd78d84bb162c98772234427a21048ee4 100644
--- a/chrome/browser/resources/md_history/history_list.js
+++ b/chrome/browser/resources/md_history/history_list.js
@@ -206,6 +206,16 @@ Polymer({
   },
 
   /**
+   * Return the number of history items to be deleted.
+   * @return {number}
+   */
+  numToBeDeleted: function() {

[tsergeant, 2016/07/19 05:09:41]

Nit: Rename this to something like numSelected or selectedCount, since that's
what you're actually counting here.

[lshang, 2016/07/20 01:19:09]

I deleted this method and used 'toolbar.count' instead, but I'll pay attention
to method's names next time. Good suggestion.

+    return this.historyData_.filter(function(item) {
+      return item.selected;
+    }).length;
+  },
+
+  /**
    * Called when the page is scrolled to near the bottom of the list.
    * @private
    */