feat(change_detection): allow triggering CD form ChangeDetectorRef

Closes #4144

modules/angular2/src/core/change_detection/change_detector_ref.ts

@@ -25,6 +25,8 @@ export class ChangeDetectorRef {
    */
   detach(): void { this._cd.mode = ChangeDetectionStrategy.Detached; }
 
+  detectChanges(): void { this._cd.detectChanges(); }
+
   /**
    * Reattach the change detector to the change detector tree.
    *

modules/angular2/test/core/change_detection/change_detector_ref_spec.ts

@@ -0,0 +1,28 @@
+import {
+  ddescribe,
+  describe,
+  it,
+  iit,
+  xit,
+  expect,
+  beforeEach,
+  afterEach,
+  tick,
+  fakeAsync
+} from 'angular2/test_lib';
+
+import {ChangeDetectorRef} from 'angular2/src/core/change_detection/change_detector_ref';
+import {SpyChangeDetector} from '../spies';
+
+
+export function main() {
+  describe('ChangeDetectorRef', () => {
+    it('should delegate detectChanges()', () => {
+      var changeDetector = new SpyChangeDetector();
+      changeDetector.spy('detectChanges');
+      var changeDetectorRef = new ChangeDetectorRef(<any>changeDetector);
+      changeDetectorRef.detectChanges();
+      expect(changeDetector.spy('detectChanges')).toHaveBeenCalled();
+    });
+  });
+}