- 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
mate::Handle<Menu> menu;
  args->GetNext(&menu);
  gfx::Point pos;
  args->GetNext(&pos);
  tray_icon_->PopUpContextMenu(pos, menu.IsEmpty() ? nullptr : menu->model());
}
void Tray::SetContextMenu(v8::Isolate* isolate, mate::Handle<Menu> menu) {
  menu_.Reset(isolate, menu.ToV8());
  tray_icon_->SetContextMenu(menu->model());
}
gfx::Rect Tray::GetBounds() {
  return tray_icon_->GetBounds();
}
void Tray::BuildPrototype(v8::Isolate* isolate,