### 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
sandbox::ResultCode result = policy->AddRule(
      sandbox::TargetPolicy::SUBSYS_FILES,
      sandbox::TargetPolicy::FILES_ALLOW_ANY, L"\\??\\pipe\\crashpad_*");
  if (result != sandbox::SBOX_ALL_OK)
    return false;
  return true;
}
#endif  
std::string AtomBrowserClient::GetApplicationLocale() {
  if (BrowserThread::CurrentlyOn(BrowserThread::IO))
    return g_io_thread_application_locale.Get();
  return *g_application_locale;
}
bool AtomBrowserClient::ShouldEnableStrictSiteIsolation() {
  
  return true;
}
}