Live GC cells at shutdown

[jdm]

<Mateon1> jdm: Run this ~20 times: ./mach run -r -z -f -x foo.html

<style type="text/css"> :root .hero-mosaicAds,
:root  
:root  
 </style>  <script type="text/javascript"> 	require([ 		'ext.wikia.adEngine.adContext' 	], function (adContext) { 		var context = adContext.getContext();  		if (context.opts.pageFairRecovery === true && !window.wgUserName) { 			/* observer-7.0.2 */eval(atob("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"));  		} 	}
 );
 </script>

[jdm]

Original testcase loaded https://ipfs.io/ipfs/QmPiGRTKZLuHwxxCAjARy2MxW2ZQRY4QLMQFHRvbVQFLFh/index.html and the network I/O might be important to reproduce this.