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..284d92a11008a53390d5f0712caa68375d7217bf 100644
--- a/chrome/test/data/webui/polymer_browser_test_base.js
+++ b/chrome/test/data/webui/polymer_browser_test_base.js
@@ -95,3 +95,29 @@ 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) {

[Dan Beam, 2015/09/11 21:49:12]

initialize lastPromise_ to Promise.resolve(), remove if
(!PolymerTest.lastPromise_)

[michaelpg, 2015/09/13 03:01:05]

nice!

+  if (!PolymerTest.lastPromise_) {
+    PolymerTest.lastPromise_ = new Promise(function(resolve) {
+      setTimeout(fn);
+      setTimeout(resolve);
+    });
+  } else {
+    PolymerTest.lastPromise_ = PolymerTest.lastPromise_.then(function() {
+      return new Promise(function(resolve) {
+        setTimeout(fn);
+        setTimeout(resolve);
+      });
+    });
+  }
+  // Return a helper function of the same name which adds this function to the
+  // Promise chain.
+  return {
+    async: PolymerTest.async
+  };

[Dan Beam, 2015/09/11 21:49:12]

wat?  why not?

  return PolymerTest.lastPromise_;

so callers can chain?

[michaelpg, 2015/09/13 03:01:05]

Done. this was just sugar.

+};