[MD History] Add shift-selection to the history lists.

chrome/browser/resources/md_history/list_container.js

Index: chrome/browser/resources/md_history/list_container.js
diff --git a/chrome/browser/resources/md_history/list_container.js b/chrome/browser/resources/md_history/list_container.js
index 6cc6518d31bd4c0f1d2988c936e23d6967f80f10..9aabcca42f6f9b9299b06a6163a094de24132aa6 100644
--- a/chrome/browser/resources/md_history/list_container.js
+++ b/chrome/browser/resources/md_history/list_container.js
@@ -86,6 +86,10 @@ Polymer({
     ]);
   },
 
+  getSelectedItemCount: function() {

[tsergeant, 2016/08/15 04:49:50]

/** @return {number} */ 

[calamity, 2016/08/15 07:18:40]

Done.

+    return this.getSelectedList_().selectedPaths.size;
+  },
+
   unselectAllItems: function(count) {
     this.getSelectedList_().unselectAllItems(count);
   },