Added better error and OAuth support in xhr.js.

remoting/webapp/js_proto/sinon_proto.js

Index: remoting/webapp/js_proto/sinon_proto.js
diff --git a/remoting/webapp/js_proto/sinon_proto.js b/remoting/webapp/js_proto/sinon_proto.js
index 9e223dc8eecc1afa9cf852c8dce89f32402e0f4d..a34d76aff4c913f490b452d34bacfa181401c25b 100644
--- a/remoting/webapp/js_proto/sinon_proto.js
+++ b/remoting/webapp/js_proto/sinon_proto.js
@@ -127,12 +127,23 @@ sinon.TestStub.prototype.onFirstCall = function() {};
 /** @returns {Object}  */
 sinon.createStubInstance = function (/** * */ constructor) {};
 
-/** @return {sinon.FakeXhr} */
+/** @interface */
+sinon.FakeXhrCtrl = function() {};
+
+/**
+ * @type {?function(!sinon.FakeXhr)}
+ */
+sinon.FakeXhrCtrl.prototype.onCreate;
+
+/** @return {sinon.FakeXhrCtrl} */
 sinon.useFakeXMLHttpRequest = function() {};
 
 /** @interface */
 sinon.FakeXhr = function() {};
 
+/** @type {number} */
+sinon.FakeXhr.prototype.readyState;
+
 /** @type {string} */
 sinon.FakeXhr.prototype.method;
 
@@ -156,6 +167,7 @@ sinon.FakeXhr.prototype.requestHeaders;
 sinon.FakeXhr.prototype.respond;
 
 /**
- * @type {?function(!sinon.FakeXhr)}
+ * @param {string} event
+ * @param {Function} handler
  */
-sinon.FakeXhr.prototype.onCreate;
+sinon.FakeXhr.prototype.addEventListener;