function clearListener(){
		if (this.bRegistered) {
			this.bRegistered = false;
			IntervalTrigger.removeListener(this.checkSizes, this);
		}
	}
The block below is not needed because it only did a cleanup
before the page was closed. This should not be necessary.
Nevertheless we leave the coding here and only deprecate it,
in order to keep the BFCache behavior stable.
Removing the 'unload' handler could potentially activate
the BFCache and cause a different behavior in browser versions
where the 'unload' handler is still supported.
Therefore we only removed the not needed cleanup coding
but still attach a noop to ensure this handler would still
invalidate the BFCache.
@deprecated as of 1.119