feat(perf): change detection profiler

Closes #4000

modules/angular2/src/core/facade/browser.ts

@@ -7,6 +7,7 @@ export {win as window};
 export var document = window.document;
 export var location = window.location;
 export var gc = window['gc'] ? () => window['gc']() : () => null;
+export var performance = window['performance'] ? window['performance'] : null;
 export const Event = Event;
 export const MouseEvent = MouseEvent;
 export const KeyboardEvent = KeyboardEvent;