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

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

Index: chrome/test/data/webui/md_bookmarks/app_test.js
diff --git a/chrome/test/data/webui/md_bookmarks/app_test.js b/chrome/test/data/webui/md_bookmarks/app_test.js
index 80e3baea52ab8b2e5815253506e1be1d5a8975fc..8ea1bc76efbde78e9c41a246dbe263f6c5984500 100644
--- a/chrome/test/data/webui/md_bookmarks/app_test.js
+++ b/chrome/test/data/webui/md_bookmarks/app_test.js
@@ -38,13 +38,14 @@ suite('<bookmarks-app>', function() {
   });
 
   test('write and load closed folder state', function() {
-    var closedFolders = {'1': true};
+    var closedFoldersList = ['1'];
+    var closedFolders = new Set(closedFoldersList);
     store.data.closedFolders = closedFolders;
     store.notifyObservers();
 
     // Ensure closed folders are written to local storage.
     assertDeepEquals(
-        JSON.stringify(closedFolders),
+        JSON.stringify(Array.from(closedFolders)),
         window.localStorage[LOCAL_STORAGE_CLOSED_FOLDERS_KEY]);
 
     resetStore();
@@ -52,6 +53,6 @@ suite('<bookmarks-app>', function() {
     replaceBody(app);
 
     // Ensure closed folders are read from local storage.
-    assertDeepEquals(closedFolders, store.data.closedFolders);
+    assertDeepEquals(closedFoldersList, normalizeSet(store.data.closedFolders));
   });
 });