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]
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.
Created attachment 43113 [details]
Comment on attachment 43113 [details]
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.