Convert Google Now's Authentication Manager to use Promises

chrome/browser/resources/google_now/common_test_util.js

Index: chrome/browser/resources/google_now/common_test_util.js
diff --git a/chrome/browser/resources/google_now/common_test_util.js b/chrome/browser/resources/google_now/common_test_util.js
index 754e2578fa2f6bf059a5b2b70fbb7ea8c6ed0bed..44d21e6d1f640ea07406a7919738959bcbb09706 100644
--- a/chrome/browser/resources/google_now/common_test_util.js
+++ b/chrome/browser/resources/google_now/common_test_util.js
@@ -82,16 +82,35 @@ function getMockHandlerContainer(eventIdentifier) {
 var Promise = function() {
   function PromisePrototypeObject(asyncTask) {
     var result;
+    var resolved = false;
     asyncTask(
         function(asyncResult) {
           result = asyncResult;
+          resolved = true;
         },
-        function() {}); // Errors are unsupported.
+        function(asyncFailureResult) {
+          result = asyncFailureResult;
+          resolved = false;
+        });
 
     function then(callback) {
-      callback.call(null, result);
+      if (resolved) {
+        callback.call(null, result);
+      }
+      return this;
+    }
+
+    // Promises use the function name "catch" to call back error handlers.
+    // We can't use "catch" since function or variable names cannot use the word
+    // "catch".
+    function catchFunc(callback) {
+      if (!resolved) {
+        callback.call(null, result);
+      }
+      return this;
     }
-    return {then: then, isPromise: true};
+
+    return {then: then, catch: catchFunc, isPromise: true};
   }
 
   function all(arrayOfPromises) {