I noticed this when I was working for Bug 100922. This might cause mysterious errors in future.
The root cause seems HTMLMediaElement creates Shadow subtree in insertedInto().
This seems a bad signal...
(In reply to comment #1)
> The root cause seems HTMLMediaElement creates Shadow subtree in insertedInto().
> This seems a bad signal...
It sounds reasonable to get rid of the shadow construction from insertedInto().
I'm not sure where is the best place though.
It needs further investigation.
Yeah, this is crufty. insertedInto is a really low-level hook, and it's tempting to use it various convenient purposes. However, being a low-level hook, it's also a minefield in situations like this.
configureMediaControls() is now called in HTMLMediaElement::didFinishInsertingNode() so this is no longer happening.