- 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/api/atom_api_tray.h
void OnClicked(const gfx::Rect& bounds, int modifiers) override;
  void OnDoubleClicked(const gfx::Rect& bounds, int modifiers) override;
  void OnRightClicked(const gfx::Rect& bounds, int modifiers) override;
  void OnBalloonShow() override;
  void OnBalloonClicked() override;
  void OnBalloonClosed() override;
  void OnDrop() override;
  void OnDropFiles(const std::vector<std::string>& files) override;
  void OnDropText(const std::string& text) override;
  void OnDragEntered() override;
  void OnDragExited() override;
  void OnDragEnded() override;
  void SetImage(v8::Isolate* isolate, mate::Handle<NativeImage> image);
  void SetPressedImage(v8::Isolate* isolate, mate::Handle<NativeImage> image);
  void SetToolTip(const std::string& tool_tip);
  void SetTitle(const std::string& title);
  void SetHighlightMode(TrayIcon::HighlightMode mode);
  void DisplayBalloon(mate::Arguments* args, const mate::Dictionary& options);
  void PopUpContextMenu(mate::Arguments* args);
  void SetContextMenu(v8::Isolate* isolate, mate::Handle<Menu> menu);
  gfx::Rect GetBounds();
 private:
  v8::Global<v8::Object> menu_;
  std::unique_ptr<TrayIcon> tray_icon_;
  DISALLOW_COPY_AND_ASSIGN(Tray);
};
}  
}  
#endif