Mismatched acceleration settings == terrible performance.
Created attachment 237419 [details]
Attachment 237419 [details] did not pass style-queue:
ERROR: Source/WebCore/ChangeLog:1: ChangeLog entry has no bug number [changelog/bugnumber] 
Total errors found: 1 in 2 files
If any of these errors are false positives, please file a bug against check-webkit-style.
Comment on attachment 237419 [details]
Any way to test this? Is this a performance enhancement or something else?
Just performance, no way to test (unless we were to add some mechanism to log when someone paints from an unaccelerated buffer to an accelerated context or vice versa, and then wrote some tests around that).