refactor(): use const and let instead of var

modules/@angular/examples/testing/ts/fake_async.ts

@@ -12,7 +12,7 @@ import {discardPeriodicTasks, fakeAsync, tick} from '@angular/core/testing';
 // #docregion basic
 describe('this test', () => {
   it('looks async but is synchronous', <any>fakeAsync((): void => {
-       var flag = false;
+       let flag = false;
        setTimeout(() => { flag = true; }, 100);
        expect(flag).toBe(false);
        tick(50);

modules/@angular/examples/testing/ts/testing.ts

@@ -8,7 +8,7 @@
 
 import {afterEach, beforeEach, beforeEachProviders, describe, inject, it, xdescribe, xit} from '@angular/core/testing/testing_internal';
 
-var db: any;
+let db: any;
 class MyService {}
 class MyMockService implements MyService {}