* 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
#include "atom/browser/net/url_request_context_getter.h"
#include <algorithm>
#include <memory>
#include <utility>
#include "atom/browser/api/atom_api_protocol.h"
#include "atom/browser/atom_browser_client.h"
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/browser_process_impl.h"
#include "atom/browser/net/about_protocol_handler.h"
#include "atom/browser/net/asar/asar_protocol_handler.h"
#include "atom/browser/net/atom_cert_verifier.h"
#include "atom/browser/net/atom_network_delegate.h"
#include "atom/browser/net/atom_url_request_job_factory.h"
#include "atom/browser/net/http_protocol_handler.h"
#include "atom/browser/net/require_ct_delegate.h"
#include "atom/browser/net/system_network_context_manager.h"
#include "base/command_line.h"
#include "base/strings/string_util.h"
#include "base/task_scheduler/post_task.h"
#include "chrome/common/chrome_constants.h"
#include "chrome/common/pref_names.h"
#include "components/network_session_configurator/common/network_switches.h"
#include "components/prefs/value_map_pref_store.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/devtools_network_transaction_factory.h"
#include "content/public/browser/network_service_instance.h"
#include "content/public/browser/resource_context.h"
#include "net/base/host_mapping_rules.h"
#include "net/cert/multi_log_ct_verifier.h"