* Electron version: 1.7.6
* Operating system: MacOS High Sierra GM

### Expected behavior

Title bar should not be invisible

![screen shot 2017-09-14 at 11 22 04 am](https://user-images.githubusercontent.com/320654/30441406-f34fe61a-993e-11e7-8592-244e50a92bb9.png)

### Actual behavior

Title bar is invisible

### How to reproduce
```
  mainWindow = new BrowserWindow({
      vibrancy: 'light',
      titleBarStyle: 'hiddenInset',
      width: 800,
      height: 600
  })
```

```
 $ git clone git@github.com:gerges/electron-quick-start.git -b  issue/invisible-titlebar
 $ npm install
 $ npm run start
```

atom/browser/native_window_mac.h
void Restore() override;
  bool IsMinimized() override;
  void SetFullScreen(bool fullscreen) override;
  bool IsFullscreen() const override;
  void SetBounds(const gfx::Rect& bounds, bool animate = false) override;
  gfx::Rect GetBounds() override;
  void SetContentSizeConstraints(
      const extensions::SizeConstraints& size_constraints) override;
  void SetResizable(bool resizable) override;
  bool IsResizable() override;
  void SetMovable(bool movable) override;
  void SetAspectRatio(double aspect_ratio, const gfx::Size& extra_size)
    override;
  void PreviewFile(const std::string& path, const std::string& display_name)
    override;
  void CloseFilePreview() override;
  bool IsMovable() override;
  void SetMinimizable(bool minimizable) override;
  bool IsMinimizable() override;
  void SetMaximizable(bool maximizable) override;
  bool IsMaximizable() override;
  void SetFullScreenable(bool fullscreenable) override;
  bool IsFullScreenable() override;
  void SetClosable(bool closable) override;
  bool IsClosable() override;
  void SetAlwaysOnTop(bool top, const std::string& level,
                      int relativeLevel, std::string* error) override;
  bool IsAlwaysOnTop() override;
  void Center() override;
  void Invalidate() override;