fix: add types for ts2dart's façade handling.

... in many, many places.

modules/angular2/test/render/xhr_impl_spec.ts

@@ -15,7 +15,7 @@ import {PromiseWrapper} from 'angular2/src/facade/async';
 
 export function main() {
   describe('XHRImpl', () => {
-    var xhr;
+    var xhr: XHRImpl;
     var url200 = '/base/modules/angular2/test/services/static_assets/200.html';
     var url404 = '/base/modules/angular2/test/services/static_assets/404.html';
 
@@ -33,6 +33,7 @@ export function main() {
          PromiseWrapper.catchError(xhr.get(url404), (e) => {
            expect(e).toEqual(`Failed to load ${url404}`);
            async.done();
+           return null;
          });
        }));
   });

modules/angular2/test/render/xhr_mock_spec.ts

@@ -16,7 +16,7 @@ import {isPresent} from 'angular2/src/facade/lang';
 
 export function main() {
   describe('MockXHR', () => {
-    var xhr;
+    var xhr: MockXHR;
 
     beforeEach(() => { xhr = new MockXHR(); });