* 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
root_view_->SetAutoHideMenuBar(auto_hide);
}
bool NativeWindowViews::IsMenuBarAutoHide() {
  return root_view_->IsMenuBarAutoHide();
}
void NativeWindowViews::SetMenuBarVisibility(bool visible) {
  root_view_->SetMenuBarVisibility(visible);
}
bool NativeWindowViews::IsMenuBarVisible() {
  return root_view_->IsMenuBarVisible();
}
void NativeWindowViews::SetVisibleOnAllWorkspaces(bool visible,
                                                  bool visibleOnFullScreen) {
  widget()->SetVisibleOnAllWorkspaces(visible);
}
bool NativeWindowViews::IsVisibleOnAllWorkspaces() {
#if defined(USE_X11)
  
  
  XAtom sticky_atom = GetAtom("_NET_WM_STATE_STICKY");
  std::vector<XAtom> wm_states;
  ui::GetAtomArrayProperty(GetAcceleratedWidget(), "_NET_WM_STATE", &wm_states);
  return std::find(wm_states.begin(), wm_states.end(), sticky_atom) !=
         wm_states.end();
#endif
  return false;
}
gfx::AcceleratedWidget NativeWindowViews::GetAcceleratedWidget() const {