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### Preflight Checklist
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* [X ] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [X ] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [X ] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details
This is a bug report specifically for the 7.0 beta. 

* **Electron Version:**
  * 7.0.0-beta.6
* **Operating System:**
  * Ubuntu 18.04 x64, Windows 10
* **Last Known Working Electron version:**
  * 6.0.12

### Expected Behavior
SharedWorker should be functional and *shared* when using
  a custom protocol to provide a proper origin.

### Actual Behavior
SharedWorker does not execute when loaded from custom protocol.
It does execute when page is loaded with the `file://` protocol, but this 
  defeats the purpose, since it is not shared between contexts.

Also noticed while diagnosing the issue:
Creating a SharedWorker with node integration enabled using a Data URL crashes 
the renderer.  I verified that this works in Electron 6, figured the cause might be related.

### To Reproduce
Install and run the following repo:

https://github.com/krisdages/electron-7-shared-worker-broken

$ git clone https://github.com/krisdages/electron-7-shared-worker-broken
$ npm install
$ npm start

Sorry, had it implemented before seeing the "electron fiddle" option. May try that next time.

Thanks for looking into this :)
shell/browser/electron_browser_client.cc
return nullptr;
}
void ElectronBrowserClient::OverrideWebkitPrefs(
    content::RenderViewHost* host,
    content::WebPreferences* prefs) {
  prefs->javascript_enabled = true;
  prefs->web_security_enabled = true;
  prefs->plugins_enabled = true;
  prefs->dom_paste_enabled = true;
  prefs->allow_scripts_to_close_windows = true;
  prefs->javascript_can_access_clipboard = true;
  prefs->local_storage_enabled = true;
  prefs->databases_enabled = true;
  prefs->application_cache_enabled = true;
  prefs->allow_universal_access_from_file_urls = true;
  prefs->allow_file_access_from_file_urls = true;
  prefs->webgl1_enabled = true;
  prefs->webgl2_enabled = true;
  prefs->allow_running_insecure_content = false;
  prefs->default_minimum_page_scale_factor = 1.f;
  prefs->default_maximum_page_scale_factor = 1.f;
  prefs->navigate_on_drag_drop = false;
#if !BUILDFLAG(ENABLE_PICTURE_IN_PICTURE)
  prefs->picture_in_picture_enabled = false;
#endif
  ui::NativeTheme* native_theme = ui::NativeTheme::GetInstanceForNativeUi();
  prefs->preferred_color_scheme = native_theme->ShouldUseDarkColors()
                                      ? blink::PreferredColorScheme::kDark