### 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.h
#ifndef SHELL_BROWSER_ATOM_BROWSER_CLIENT_H_
#define SHELL_BROWSER_ATOM_BROWSER_CLIENT_H_
#include <map>
#include <memory>
#include <set>
#include <string>
#include <vector>
#include "base/synchronization/lock.h"
#include "content/public/browser/content_browser_client.h"
#include "content/public/browser/render_process_host_observer.h"
#include "net/ssl/client_cert_identity.h"
namespace content {
class QuotaPermissionContext;
class ClientCertificateDelegate;
}  
namespace net {
class SSLCertRequestInfo;
}
namespace electron {
class NotificationPresenter;