[MD History] Refactor history.html into a history-app element.

chrome/test/data/webui/md_history/history_item_test.js

Index: chrome/test/data/webui/md_history/history_item_test.js
diff --git a/chrome/test/data/webui/md_history/history_item_test.js b/chrome/test/data/webui/md_history/history_item_test.js
index 6d6691b4bf98a621ec12ab7de881357a4d520904..c65e8d6fa4e13df1241921da2d73517a3a4aae9b 100644
--- a/chrome/test/data/webui/md_history/history_item_test.js
+++ b/chrome/test/data/webui/md_history/history_item_test.js
@@ -10,7 +10,7 @@ cr.define('md_history.history_item_test', function() {
       var SEARCH_HISTORY_RESULTS;
 
       suiteSetup(function() {
-        element = $('history-list');
+        element = $('history-app').$['history-list'];
         TEST_HISTORY_RESULTS = [
           createHistoryEntry('2016-03-16 10:00', 'http://www.google.com'),
           createHistoryEntry('2016-03-16 9:00', 'http://www.example.com'),