To reproduce, launch Chromium with --force-compositing-mode --enable-threaded-compositing.
Open http://diden.net/test/tex.html in two tabs and switch back and forth between them. Both tabs hit an assert fairly quickly:
ASSERTION FAILED: m_needsCommit
third_party/WebKit/Source/WebCore/platform/graphics/chromium/cc/CCSchedulerStateMachine.cpp(109) : void WebCore::CCSchedulerStateMachine::updateState(WebCore::CCSchedulerStateMachine::Action)
Can't seem to get a full stack trace, even with --disable-seccomp-sandbox.
This looks a lot like what https://bugs.webkit.org/show_bug.cgi?id=73351 fixed in http://trac.webkit.org/changeset/101911 - is your build out of date?
Hmm, shouldn't be, as I was hitting it on ToT synced today. I reproduced on a straight Chrome build, though, so maybe its WebKit is slightly behind.
Is the version of WebKit you are testing earlier than 101911 (it's in about:version)?
Just checked the actual code, I don't have that patch yet.
I'll see if I can find a different repro case, or close this if not.
OK. The repro steps don't happen for me with that patch, so I'm going to presume this is fixed. Feel free to reopen or file a new bug if you find a case that's still broken.