Add a footer about other forms of history to the MD history page.

chrome/browser/resources/md_history/app.js

Index: chrome/browser/resources/md_history/app.js
diff --git a/chrome/browser/resources/md_history/app.js b/chrome/browser/resources/md_history/app.js
index 6d3f5d4e2d111d016111463a05fa1550b1bec366..205cae2d4611a1ced164d0339653a0b06a704711 100644
--- a/chrome/browser/resources/md_history/app.js
+++ b/chrome/browser/resources/md_history/app.js
@@ -77,6 +77,13 @@ Polymer({
   },
 
   /**
+   * @return {HistorySideBarElement} The side bar of this history app.
+   */
+  getSideBar: function() {
+    return this.$['side-bar'];
+  },
+
+  /**
    * Listens for call to cancel selection and loops through all items to set
    * checkbox to be unselected.
    * @private