* 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
public:
  ResourceContext() = default;
  ~ResourceContext() override = default;
  net::URLRequestContext* GetRequestContext() override {
    return request_context_;
  }
 private:
  friend class URLRequestContextGetter;
  net::URLRequestContext* request_context_ = nullptr;
  DISALLOW_COPY_AND_ASSIGN(ResourceContext);
};
URLRequestContextGetter::Handle::Handle(
    base::WeakPtr<AtomBrowserContext> browser_context)
    : resource_context_(new ResourceContext),
      browser_context_(browser_context),
      initialized_(false) {}
URLRequestContextGetter::Handle::~Handle() {}
content::ResourceContext*