An easy way to check this out is to handle onNavigationRequested on MiniBrowser for example. I`ve added a small diff that adds this feature on MiniBrowser. In order to crash it, just click with middle button on any link. You'll see the following output:
We are supposed to start a download.
WARNING: The web process experienced a crash on 'http://www.google.com.br/'.
Created attachment 119262 [details]
This adds simple handler to navigation request on MiniBrowser, so you can see it crashing.
Backtrace shows that this is not related to the Download code path itself but to ResouceRequest and ThirdPartyCookies. IIRC, this has been recently refactored by Simon. I will talk to him.
#0 0x00007f59a4c1bd1a in WebCore::thirdPartyCookiePolicyPermits Source/WebCore/platform/qt/ThirdPartyCookiesQt.cpp:65
#1 0x00007f59a4c0829d in WebCore::ResourceRequest::toNetworkRequest Source/WebCore/platform/network/qt/ResourceRequestQt.cpp:83
#2 0x00007f59a407ce55 in WebKit::Download::start
Created attachment 119301 [details]
Comment on attachment 119301 [details]
Clearing flags on attachment: 119301
Committed r102926: <http://trac.webkit.org/changeset/102926>
All reviewed patches have been landed. Closing bug.