[MD Bookmarks] Add Select for Bookmarks.

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

Index: chrome/test/data/webui/md_bookmarks/test_util.js
diff --git a/chrome/test/data/webui/md_bookmarks/test_util.js b/chrome/test/data/webui/md_bookmarks/test_util.js
index 64755a2f3ce1fea25e9bf214a2f6f3a405a74ad3..9e4a86a328259809c1eca59b32ade7402f214939 100644
--- a/chrome/test/data/webui/md_bookmarks/test_util.js
+++ b/chrome/test/data/webui/md_bookmarks/test_util.js
@@ -69,3 +69,14 @@ function createItem(id, config) {
   }
   return newItem;
 }
+
+/**
+ * Sends a custom click event to |element|.
+ * @param {HTMLElement} element
+ * @param {Object} config
+ */
+function customClick(element, config) {

[calamity, 2017/01/17 06:12:22]

I would fill out config with a useful set of defaults just in case and then copy
things from the arg. See history's test_util.js:shiftClick for an example of
sane defaults.

[jiaxi, 2017/01/20 04:51:09]

Done.

+  element.dispatchEvent(new MouseEvent('mousedown', config));
+  element.dispatchEvent(new MouseEvent('mouseup', config));
+  element.dispatchEvent(new MouseEvent('click', config));
+}