void _ensureKeepAlive()
{
D.assert(this._keepAliveHandle == null);
this._keepAliveHandle = new KeepAliveHandle();
new KeepAliveNotification(this._keepAliveHandle).dispatch(this.context);
}
void _releaseKeepAlive()
{
this._keepAliveHandle.release();
this._keepAliveHandle = null;
}
void _releaseKeepAlive()
{
_keepAliveHandle.release();
_keepAliveHandle = null;
}