looseMock(toMock, ignoreUnexpectedCalls = false) {
    if (!this.shouldMakeMockControl_) {
      throw new Error(
          'MockControl not available on this environment. ' +
          'Call withMockControl if this environment is expected ' +
          'to contain a MockControl.');
    }
    const mock =
        this.mockControl.createLooseMock(toMock, ignoreUnexpectedCalls);
    // Mocks are not type-checkable. To reduce burden on tests that are type
    // checked, this is typed as "?" to turn off JSCompiler checking.
    // TODO(user): Enable a type-checked mocking library.
    return /** @type {?} */ (mock);
  }
Creates a basic loose mock of a `toMock`. For more advanced mocking,
please use the MockControl directly.
@param {?Function|?Object} toMock
@param {boolean=} ignoreUnexpectedCalls Defaults to false.
@return {?}