* 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/api/atom_api_top_level_window.cc
base::string16 app_id;
  base::FilePath app_icon_path;
  int app_icon_index = 0;
  base::string16 relaunch_command;
  base::string16 relaunch_display_name;
  options.Get("appId", &app_id);
  options.Get("appIconPath", &app_icon_path);
  options.Get("appIconIndex", &app_icon_index);
  options.Get("relaunchCommand", &relaunch_command);
  options.Get("relaunchDisplayName", &relaunch_display_name);
  ui::win::SetAppDetailsForWindow(app_id, app_icon_path, app_icon_index,
                                  relaunch_command, relaunch_display_name,
                                  window_->GetAcceleratedWidget());
}
#endif
int32_t TopLevelWindow::GetID() const {
  return weak_map_id();
}
void TopLevelWindow::ResetBrowserView() {
  if (browser_view_.IsEmpty())
    return;
  mate::Handle<BrowserView> browser_view;
  if (mate::ConvertFromV8(isolate(), GetBrowserView(), &browser_view) &&
      !browser_view.IsEmpty()) {
    browser_view->web_contents()->SetOwnerWindow(nullptr);
  }
  browser_view_.Reset();
}
void TopLevelWindow::RemoveFromParentChildWindows() {