### Issue Details

* **Electron Version:**
  * 3.x, 4.x, 5.x, 6.x
* **Operating System:**
  * All
* **Last Known Working Electron version:**:
  * 2.x

### Expected Behavior
When navigations occur, a new process should be created for the navigation.

### Actual Behavior
When a navigation occurs _during_ a preloads scripts execution the same process is re-used as Chromium does not think the navigation has been committed yet.  This causes a memory leak and all native node modules to break.

### To Reproduce
Fiddle: https://gist.github.com/MarshallOfSound/c89aa0037c3da114d44aa3a2d1a0fc24

### Screenshots
![image](https://user-images.githubusercontent.com/6634592/55097842-eb45dd00-5079-11e9-99bf-d49c0d997bca.png)

As you can see here there are three navigation loads, the second and the third one actually have the same process ID (and are running in the same process)
shell/browser/atom_browser_client.cc
const service_manager::Identity& identity,
    base::CommandLine* command_line) {
#if defined(OS_MACOSX)
  if (identity.name() == audio::mojom::kServiceName)
    command_line->AppendSwitch(::switches::kMessageLoopTypeUi);
#endif
}
void AtomBrowserClient::DidCreatePpapiPlugin(content::BrowserPpapiHost* host) {
#if BUILDFLAG(ENABLE_PEPPER_FLASH)
  host->GetPpapiHost()->AddHostFactoryFilter(
      base::WrapUnique(new ChromeBrowserPepperHostFactory(host)));
#endif
}
std::string AtomBrowserClient::GetGeolocationApiKey() {
  std::unique_ptr<base::Environment> env(base::Environment::Create());
  std::string api_key;
  env->GetVar("GOOGLE_API_KEY", &api_key);
  return api_key;
}
scoped_refptr<content::QuotaPermissionContext>