- 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
}
namespace mate {
class Arguments;
class Dictionary;
}
namespace atom {
class TrayIcon;
namespace api {
class Menu;
class NativeImage;
class Tray : public mate::TrackableObject<Tray>,
             public TrayIconObserver {
 public:
  static mate::WrappableBase* New(mate::Handle<NativeImage> image,
                                  mate::Arguments* args);
  static void BuildPrototype(v8::Isolate* isolate,
                             v8::Local<v8::FunctionTemplate> prototype);
 protected:
  Tray(v8::Isolate* isolate, v8::Local<v8::Object> wrapper,
       mate::Handle<NativeImage> image);
  ~Tray() override;