ASSERTION FAILED: !s.escaped() in Webkit

Using the webbrowser example in debug and navigating to the website: https://plus.google.com/+BarackObama/posts make it crash with assertion:

ASSERTION FAILED: !s.escaped()
platform\text\SegmentedString.cpp(169) : void WebCore::SegmentedString::append(const WebCore::SegmentedString&)
1 14DE6F9D
2 14E0629F

I'm using Qt 5.3.1 with MinGW (GCC 4.8).

It's probably related to https://code.google.com/p/chromium/issues/detail?id=345726 (the fix is probably just not reported in the current Qt version).