[MD History] Factor out a common HistoryListBehavior.

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

Index: chrome/test/data/webui/md_history/test_util.js
diff --git a/chrome/test/data/webui/md_history/test_util.js b/chrome/test/data/webui/md_history/test_util.js
index d4f44ea367b34e203deb87f11badefcbd61c5697..d9be81b7ab3ef4786dc3c5071959f37c2f04a221 100644
--- a/chrome/test/data/webui/md_history/test_util.js
+++ b/chrome/test/data/webui/md_history/test_util.js
@@ -75,3 +75,12 @@ function createHistoryInfo(searchTerm) {
     term: searchTerm || ''
   };
 }
+
+/**
+ * @param {Element} element
+ * @param {string} selector
+ * @return {Element}
+ */
+function polymerQuerySelectorAll(element, selector) {

[tsergeant, 2016/08/05 01:39:09]

If you want, you could make your/our lives easier by naming this
polymerSelectAll or something a bit shorter.

[calamity, 2016/08/09 02:56:00]

Done.

+  return Polymer.dom(element.root).querySelectorAll(selector);
+}