### 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
AtomBrowserClient::CreateQuotaPermissionContext() {
  return new AtomQuotaPermissionContext;
}
content::GeneratedCodeCacheSettings
AtomBrowserClient::GetGeneratedCodeCacheSettings(
    content::BrowserContext* context) {
  
  base::FilePath cache_path = context->GetPath();
  
  
  
  return content::GeneratedCodeCacheSettings(true, 0, cache_path);
}
void AtomBrowserClient::AllowCertificateError(
    content::WebContents* web_contents,
    int cert_error,
    const net::SSLInfo& ssl_info,
    const GURL& request_url,
    bool is_main_frame_request,
    bool strict_enforcement,
    bool expired_previous_decision,
    const base::RepeatingCallback<void(content::CertificateRequestResultType)>&
        callback) {
  if (delegate_) {
    delegate_->AllowCertificateError(
        web_contents, cert_error, ssl_info, request_url, is_main_frame_request,
        strict_enforcement, expired_previous_decision, callback);
  }
}
base::OnceClosure AtomBrowserClient::SelectClientCertificate(