[MD Bookmarks] Change selection items from Map to Set.

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 71d71563e1a0f022211fd2a5dc3bbc7751a721bb..090758749019d447ceb5c8d237dabe997b2fdeac 100644
--- a/chrome/test/data/webui/md_bookmarks/test_util.js
+++ b/chrome/test/data/webui/md_bookmarks/test_util.js
@@ -83,6 +83,15 @@ function createItem(id, config) {
 }
 
 /**
+ * @param {Set<T>}
+ * @return {Array<T>}
+ * @template T
+ */
+function normalizeSet(set) {
+  return Array.from(set).sort();
+}
+
+/**
  * Sends a custom click event to |element|.
  * @param {HTMLElement} element
  * @param {Object=} config