In r150629, the code from that change introduced to suspend and resume root layer commits would not take into account whether the page is actually visible. Because application activation state is usually conveyed to all or any WebPages, this would mean on transitioning into an active application state, we were resuming root layer commits that might have previously been disabled for visibility reasons. The patch below fixes this by going through a single function that knows by itself whether to suspend or resume root layer commits, so the calling code doesn't have a chance to get it wrong.
Created attachment 205337 [details] Patch
Comment on attachment 205337 [details] Patch This looks cleaner too.
Comment on attachment 205337 [details] Patch Clearing flags on attachment: 205337 Committed r151936: <http://trac.webkit.org/changeset/151936>
All reviewed patches have been landed. Closing bug.
Appendix: See https://bugs.webkit.org/show_bug.cgi?id=115245 for the original patch that got fixed up by this one here.