### 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::GetExtraServiceManifests() {
  return GetElectronBuiltinServiceManifests();
}
std::unique_ptr<content::BrowserMainParts>
AtomBrowserClient::CreateBrowserMainParts(
    const content::MainFunctionParams& params) {
  return std::make_unique<AtomBrowserMainParts>(params);
}
void AtomBrowserClient::WebNotificationAllowed(
    int render_process_id,
    base::OnceCallback<void(bool, bool)> callback) {
  content::WebContents* web_contents =
      WebContentsPreferences::GetWebContentsFromProcessID(render_process_id);
  if (!web_contents) {
    std::move(callback).Run(false, false);
    return;
  }
  auto* permission_helper =
      WebContentsPermissionHelper::FromWebContents(web_contents);
  if (!permission_helper) {
    std::move(callback).Run(false, false);
    return;
  }
  permission_helper->RequestWebNotificationPermission(
      base::BindOnce(std::move(callback), web_contents->IsAudioMuted()));
}
void AtomBrowserClient::RenderProcessHostDestroyed(