This happens with printing/print-close-crash.html in the GTK+ port. This is how it happens:
1. print() is called while the document is still loading, so m_shouldPrintWhenFinishedLoading is set to true
2. DataURLDecoder::decode() finishes in the work queue thread, the completion handler is scheduled in the main thread
3. The load is cancelled
3.1 SubresourceLoader::willCancel sets m_state = Finishing
3.2 DOMWindow::finishedLoading() is called, and since m_shouldPrintWhenFinishedLoading is true, it does the print.
3.3 Cancellation finishes and ResourceLoader::releaseResources() si called that sets m_reachedTerminalState = true
So, between 3.1 and 3.3, the state is finishing, but m_reachedTerminalState is false. What happens, in the GTK+ port at least, is that the nested main loop used to make print() synchronous, processes the DataURLDecoder::decode() completion handler that was pending. The completion handler returns early if m_reachedTerminalState is true, but it's not yet in this particular case. So, it ends up calling didReceiveResponse (because the decode didn't fail) when the subresource loader state is Finishing.
I think there are two things here. One is that we shouldn't start a print that was waiting for the load to finish when it failed. That would fix the problem. But it's probably a good idea to also check for cancellation in the DataURLDecoder::decode() completion handler.
Created attachment 263472 [details]
Committed r191332: <http://trac.webkit.org/changeset/191332>