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### 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
content::RenderFrameHost* rfh,
    content::SiteInstance* site_instance) {
  std::string affinity = GetAffinityPreference(rfh);
  if (!affinity.empty()) {
    site_per_affinities_[affinity] = site_instance;
  }
}
bool ElectronBrowserClient::IsRendererSubFrame(int process_id) const {
  return base::Contains(renderer_is_subframe_, process_id);
}
void ElectronBrowserClient::RenderProcessWillLaunch(
    content::RenderProcessHost* host) {
  
  int process_id = host->GetID();
  if (IsProcessObserved(process_id))
    return;
  auto* browser_context = host->GetBrowserContext();
  ALLOW_UNUSED_LOCAL(browser_context);
#if BUILDFLAG(ENABLE_PRINTING)
  host->AddFilter(
      new printing::PrintingMessageFilter(process_id, browser_context));