title: Conflict between zone.js and Jasmine's clock
body: <p>I am working with a Jasmine testing suite that includes both "vanilla" Jasmine tests along with Jasmine tests for some Angular 2 components. Because of Angular 2's inclusion, zone.js gets loaded. This creates a conflict with Jasmine's clock. For example, the following test fails with the error, <code>Error: Jasmine Clock was unable to install over custom global timer functions. Is the clock already installed?</code></p>
  
  <pre><code>describe('an async test with zone.js present', function() {
    beforeEach(function() {
      jasmine.clock().install();
    });
  
    afterEach(function() {
      jasmine.clock().uninstall();
    });
  
    it('cannot install jasmine\'s mock clock', function() {
      var callback = jasmine.createSpy('setTimeoutCallback')
      setTimeout(callback, 55);
      jasmine.clock().tick(56);
      expect(callback).toHaveBeenCalled();
    });
  })
  </code></pre>
  
  <p><a href="https://plnkr.co/edit/ib16bZNsOaE6t0RCkflN?p=preview" rel="noreferrer">Here</a> is plunker for above code.</p>
  
  <p>Short of delivering the Angular 2 tests separately from the "vanilla" tests, I am wondering what options might be available. For example, is it possible to perform the Jasmine clock's job with the zone? For example, is it possible to simulate the tick with the zone or flush all of the scheduled tasks before the assertion? </p>