### 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
speculative_rfh ? speculative_rfh->GetSiteInstance() : nullptr;
  int process_id = current_instance->GetProcess()->GetID();
  if (NavigationWasRedirectedCrossSite(browser_context, current_instance,
                                       speculative_instance, url,
                                       has_response_started)) {
    
    
    return false;
  } else if (IsRendererSandboxed(process_id)) {
    
    
    return false;
  } else if (!RendererUsesNativeWindowOpen(process_id)) {
    
    
    return true;
  } else {
    auto* web_contents = content::WebContents::FromRenderFrameHost(current_rfh);
    if (!ChildWebContentsTracker::FromWebContents(web_contents)) {
      
      
      
      
      return true;
    }
  }
  
  return !IsSameWebSite(browser_context, current_instance, url);
}
bool AtomBrowserClient::NavigationWasRedirectedCrossSite(