* Output of `node_modules/.bin/electron --version`: **v4.0.0-beta.3**
* Operating System (Platform and Version): **Windows 10**
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): **v3.0.4**

**Expected Behavior**
With electron 3, I could pass `webPreferences: {webwebSecurity: false}` to the BrowserWindow constructor (the equivalent of the `--disable-web-security` Chrome command line argument) which would disable CORB (effectively allowing cross-origin requests).

**Actual behavior**
CORB is still doing its thing (ignoring the `{webwebSecurity: false}` option; I see entries like these in the console:
`Cross-Origin Read Blocking (CORB) blocked cross-origin response <URL> with MIME type application/json. See <URL> for more details.`

**To Reproduce**
Make a request (using fetch or xhr) to a file on a different domain.
Example repo:
```
git clone  https://github.com/IAmPicard/electron-cors-repro
npm install
npm run start
```


atom/browser/atom_browser_client.cc
#include "v8/include/v8.h"
#if defined(USE_NSS_CERTS)
#include "net/ssl/client_cert_store_nss.h"
#elif defined(OS_WIN)
#include "net/ssl/client_cert_store_win.h"
#elif defined(OS_MACOSX)
#include "net/ssl/client_cert_store_mac.h"
#elif defined(USE_OPENSSL)
#include "net/ssl/client_cert_store.h"
#endif
#if BUILDFLAG(ENABLE_PEPPER_FLASH)
#include "chrome/browser/renderer_host/pepper/chrome_browser_pepper_host_factory.h"
#endif  
#if BUILDFLAG(OVERRIDE_LOCATION_PROVIDER)
#include "atom/browser/fake_location_provider.h"
#endif  
#if BUILDFLAG(ENABLE_TTS)
#include "chrome/browser/speech/tts_message_filter.h"
#endif  
#if BUILDFLAG(ENABLE_PRINTING)
#include "chrome/browser/printing/printing_message_filter.h"
#include "chrome/services/printing/public/mojom/constants.mojom.h"
#include "components/services/pdf_compositor/public/interfaces/pdf_compositor.mojom.h"
#endif  
using content::BrowserThread;
namespace atom {
namespace {
bool g_suppress_renderer_process_restart = false;
base::NoDestructor<std::string> g_custom_service_worker_schemes;
bool IsSameWebSite(content::BrowserContext* browser_context,