Add Polymer tests for cr-settings-prefs

chrome/test/data/webui/polymer_browser_test_base.js

Index: chrome/test/data/webui/polymer_browser_test_base.js
diff --git a/chrome/test/data/webui/polymer_browser_test_base.js b/chrome/test/data/webui/polymer_browser_test_base.js
index b768ef76f555a034a033641b08b6ae2c3845b7de..022c94012e31122db59e9f440b4095da6314f793 100644
--- a/chrome/test/data/webui/polymer_browser_test_base.js
+++ b/chrome/test/data/webui/polymer_browser_test_base.js
@@ -95,3 +95,27 @@ PolymerTest.getLibraries = function(basePath) {
     return basePath + library;
   });
 };
+
+/**
+ * Allows chaining asynchronous function to avoid having to write nested
+ * Promises or setTimeouts.
+ * Example: PolymerTest.async(fn1).async(fn2).async(fn3).async(done);
+ */
+PolymerTest.async = function(fn) {
+  // Wrap the asynchronous call to |fn| in a Promise.
+  var p = new Promise(function(resolve, reject) {
+    setTimeout(function() {
+      fn.call();
+      resolve();
+    });
+  });
+  // Return a helper function of the same name which adds this function to the
+  // Promise chain.
+  return {
+    async: function(fn) {
+      p.then(function() {
+        return PolymerTest.async(fn);

[michaelpg, 2015/09/08 06:26:59]

this doesn't quite work. what I actually want is something like
https://codereview.chromium.org/1333473002/diff/20001/chrome/test/data/webui/...
(not ready for review)

[michaelpg, 2015/09/11 20:14:38]

Ignore this comment, see new patch.

+      });
+    },
+  };
+};