- 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.cc
}
    
    
    bool highlight;
    if (ConvertFromV8(isolate, val, &highlight)) {
      if (highlight)
        *out = atom::TrayIcon::HighlightMode::SELECTION;
      else
        *out = atom::TrayIcon::HighlightMode::NEVER;
      return true;
    }
    return false;
  }
};
}  
namespace atom {
namespace api {
Tray::Tray(v8::Isolate* isolate, v8::Local<v8::Object> wrapper,
           mate::Handle<NativeImage> image)
    : tray_icon_(TrayIcon::Create()) {
  SetImage(isolate, image);
  tray_icon_->AddObserver(this);
  InitWith(isolate, wrapper);
}
Tray::~Tray() {
  
  base::ThreadTaskRunnerHandle::Get()->DeleteSoon(
      FROM_HERE, tray_icon_.release());
}
mate::WrappableBase* Tray::New(mate::Handle<NativeImage> image,