There is a Mac-only willCacheResponse notification that gets recorded by several of the layout tests when layoutTestController.dumpResourceLoadCallbacks(true) is called. However, this notification which originates at the ResourceHandle level is currently #if PLATFORM(MAC). I noticed that the tests which depend on this notification are currently skipped on platform/win. For Chromium, we have simply rebaselined with the willCacheResponse events excluded. Having a separate baseline is unfortunate and not running the tests on platform/win seems even worse. I wonder if it wouldn't be better to exclude willCacheResponse by default, and then only enable it selectively for tests that are about testing it. That way, we can un-skip the other tests that only fail on non-Mac as a side-effect of this notification not being supported. We could also try to support willCacheResponse on all platforms, but that seems like a lot of work for little gain. Afterall, it is a notification that WebKit doesn't itself care about. It is just something provided to the embedder of the WebKit Framework on Mac. I didn't see any bugs on file about this issue. -Darin