Load a YouTube video in MiniBrowser, start playing, then close the window. The audio keeps playing, suggesting that we've leaked the WKWebView or failed to clean something up.
The WKWebView is kept alive.
<rdar://problem/62655674>
Might want to re-check after fix for Bug 211243 lands.
No longer happens. Probably regressed at r176862 or r210483 and fixed at r261324.