- Electron version:1.3.3
- Operating system:win10/mac

the Tray instance events shold provide the tray hover event. 
`tray.setToolTip` has limitations when do more operation.

atom/browser/ui/tray_icon.h
public:
  static TrayIcon* Create();
#if defined(OS_WIN)
  using ImageType = HICON;
#else
  using ImageType = const gfx::Image&;
#endif
  virtual ~TrayIcon();
  
  virtual void SetImage(ImageType image) = 0;
  
  virtual void SetPressedImage(ImageType image);
  
  
  
  
  virtual void SetToolTip(const std::string& tool_tip) = 0;
  
  
  virtual void SetTitle(const std::string& title);
  
  enum HighlightMode {