refactor(autocomplete): switch to fakeAsync tests (#8781)

* Switches (almost) all of the autocomplete tests to run in the `fakeAsync` zone.
* Adds a `MockNgZone` provider that allows us to flush out the `NgZone.onStable` subscriptions in `fakeAsync` tests.
* Fixes the "should close the panel when the user clicks away" test not doing anything due to being wrapped in a `whenStable` callback but not running in an async zone.
* Avoids recompiling all of the test components inside a `beforeEach`.

The above-mentioned changes cut down the autocomplete testing time from ~30sec to ~10sec.

Author: crisbeto

src/cdk/testing/mock-ng-zone.ts

@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {EventEmitter, Injectable, NgZone} from '@angular/core';
+
+
+/**
+ * Mock synchronous NgZone implementation that can be used
+ * to flush out `onStable` subscriptions in tests.
+ *
+ * via: https://github.com/angular/angular/blob/master/packages/core/testing/src/ng_zone_mock.ts
+ * @docs-private
+ */
+@Injectable()
+export class MockNgZone extends NgZone {
+  onStable: EventEmitter<any> = new EventEmitter(false);
+
+  constructor() {
+    super({enableLongStackTrace: false});
+  }
+
+  run(fn: Function): any {
+    return fn();
+  }
+
+  runOutsideAngular(fn: Function): any {
+    return fn();
+  }
+
+  simulateZoneExit(): void {
+    this.onStable.emit(null);
+  }
+}

src/cdk/testing/public-api.ts

@@ -11,3 +11,4 @@ export * from './event-objects';
 export * from './type-in-element';
 export * from './wrapped-error-message';
 export * from './fake-viewport-ruler';
+export * from './mock-ng-zone';