fast/dom/Window/window-postmessage-clone.html has been failing on Windows since it was added. Apparently the Date object is getting converted to a vanilla Object when passed through postMessage.
It looks like this test is failing: if (value.isObject() && asObject(value)->inherits(&DateInstance::info)) return SerializedScriptValueData(SerializedScriptValueData::DateType, asDateInstance(value)->internalNumber()); <http://trac.webkit.org/browser/trunk/WebCore/bindings/js/SerializedScriptValue.cpp?rev=49216#L478> It seems that &DateInstance::info in WebCore and &DateInstance::info in JSC don't return the same pointer, so the inherits() test fails. I think this is a linking problem.
I think I have a fix.
Created attachment 40799 [details] Export DateInstance::info in a way that works on Windows
Committed r49247: <http://trac.webkit.org/changeset/49247>