* Output of `node_modules/.bin/electron --version`: 4.0.0-beta.5
* Operating System (Platform and Version): macOS 10.14
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): There is no issue with Electron v3.

**Expected Behavior**
Cookies should be persisted in a webview that uses partition.

**Actual behavior**
Cookies are lost after relaunching app.

**To Reproduce**
1. Create webview with partition: `<webview partition="persist:webview"/>`
2. Sign in to GitHub to create a cookie.
3. Relaunch app.
4. When webview opens again, the cookies are lost. 
atom/browser/net/url_request_context_getter.cc
cookie_schemes.insert(cookie_schemes.end(), custom_standard_schemes.begin(),
                          custom_standard_schemes.end());
    cookie_monster->SetCookieableSchemes(cookie_schemes);
    
    top_job_factory_.reset(new AtomURLRequestJobFactory);
    SetupAtomURLRequestJobFactory(&protocol_handlers_, url_request_context_,
                                  top_job_factory_.get());
    std::unique_ptr<net::URLRequestJobFactory> inner_job_factory(
        new net::URLRequestJobFactoryImpl);
    if (!protocol_interceptors_.empty()) {
      
      for (auto it = protocol_interceptors_.rbegin();
           it != protocol_interceptors_.rend(); ++it) {
        inner_job_factory.reset(new net::URLRequestInterceptingJobFactory(
            std::move(inner_job_factory), std::move(*it)));
      }
      protocol_interceptors_.clear();
    }
    top_job_factory_->Chain(std::move(inner_job_factory));
    url_request_context_->set_job_factory(top_job_factory_.get());
    context_handle_->resource_context_->request_context_ = url_request_context_;
  }
  return url_request_context_;
}
scoped_refptr<base::SingleThreadTaskRunner>
URLRequestContextGetter::GetNetworkTaskRunner() const {
  return BrowserThread::GetTaskRunnerForThread(BrowserThread::IO);
}
}