Created attachment 43092 [details] a project that demonstrates this crash. Crash when a CSS transition is run on a CSS transform in a GC supported or GC required build.
Created attachment 43101 [details] Crash log Thread 0 Crashed: Dispatch queue: com.apple.main-thread 0 com.apple.CoreFoundation 0x00007fff8399a788 CFRetain + 200 1 com.apple.QuartzCore 0x00007fff81c01a98 -[CALayer setSublayers:] + 486 2 com.apple.WebCore 0x0000000100acfcc1 WebCore::GraphicsLayerCA::updateSublayerList() + 433 (GraphicsLayerCA.mm:894) 3 com.apple.WebCore 0x0000000100ad61e8 WebCore::GraphicsLayerCA::commitLayerChanges() + 904 (GraphicsLayerCA.mm:805)
The workaround is to turn off GC in your app, for now.
<rdar://problem/7390716>
Created attachment 43113 [details] Patch
Comment on attachment 43113 [details] Patch I think it would be nice to be a little more explicit about what the bug is in the comment. Specifically, say that setSublayers:nil causes a crash.
http://trac.webkit.org/changeset/50918