testSend_streaming() {
    fetchMock(new Request('https://www.google.com', {
      headers: new Headers(),
      method: 'POST',
    })).$returns(Promise.resolve(createSuccessStreamingResponse()));

    mockControl.$replayAll();
    return verifySend(
        'POST', 200 /* expectedStatusCode */, true /* isStream */);
  }
Tests that streaming responses are properly handled.
@return {!Promise<void>}