Report from rniwa@apple.com

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Hi,

It looks like both WebKit and Blink have a problem where we end up collecting JS wrappers of slot elements enqueued for a slotchange event

You can see that this test case fails on both Safari & Chrome where it passes always on Firefox:
https://bug-167652-attachments.webkit.org/attachment.cgi?id=350479
(You may need to reload multiple times / tweak the numbers in the test to reproduce the issue on Chrome)

I was under the impression that oilpan solved all these wrapper lifecycle related issues but perhaps you still manually keep JS wrappers alive?

If so, you probably want to make sure you don’t have the same bug for custom element reaction queues as we did in WebKit:
https://trac.webkit.org/browser/webkit/trunk/LayoutTests/fast/custom-elements/custom-elements-reaction-queue-retains-js-wrapper.html?rev=236376
Again, you might need to tweak the test to induce the issue in Chrome if one exists.