* Output of `node_modules/.bin/electron --version`: 4.0.0-beta.8
* Operating System (Platform and Version): Windows 10 1803
* Output of `node_modules/.bin/electron --version` on last known working Electron version (if applicable): 4.0.0-beta.7

**Expected Behavior**
`BrowserWindow.getNativeWindowHandle()` should return different value for different window

**Actual behavior**
`BrowserWindow.getNativeWindowHandle()` returns same value for different window, which is not true nativeWindowHandle for any of them.

**To Reproduce**
Open two `BrowserWindow`, and run `getNativeWindowHandle` on both `BrowserWindow`
```js
const { remote } = require('electron')
w1 = new remote.BrowserWindow()
w2 = new remote.BrowserWindow()
console.log(w1.getNativeWindowHandle(), w2.getNativeWindowHandle())
```
![image](https://user-images.githubusercontent.com/8194131/49328509-7411a800-f5b5-11e8-9a24-827aa589d937.png)


atom/browser/native_window_views.cc
widget()->Restore();
}
bool NativeWindowViews::IsMinimized() {
  return widget()->IsMinimized();
}
void NativeWindowViews::SetFullScreen(bool fullscreen) {
  if (!IsFullScreenable())
    return;
#if defined(OS_WIN)
  
  bool leaving_fullscreen = IsFullscreen() && !fullscreen;
  if (fullscreen) {
    last_window_state_ = ui::SHOW_STATE_FULLSCREEN;
    NotifyWindowEnterFullScreen();
  } else {
    last_window_state_ = ui::SHOW_STATE_NORMAL;
    NotifyWindowLeaveFullScreen();
  }
  
  
  if (!thick_frame_) {
    if (fullscreen) {
      restore_bounds_ = GetBounds();
      auto display =