SIGABRT when running Qt5Webkitwidgets-examples on directfb platform

When running the fancybrowser example on a TI AM1808 platform with directfb platform plugin, the application crashes when drawing the ToolButtonLabel widget. I have also noticed crashes when drawing the horizontal scrollbar.

The following assertion failed
ASSERT: "!qFuzzyIsNull(c)" in file ../../include/QtCore/../../src/corelib/tools/qsize.h, line 190
The evaluated expression was "pmSize = pm.size() / pm.devicePixelRatio();" were pm is a newly created Pixmap.

In my opinion, m_devicePixelRatio should be initialized at QBlittablePlatformPixmap constructor in src/gui/image3qpixmap_blitter.cpp and updated when creating a Pixmap from an Qimage. I will submit a patch through gerrit.

Also QBlittablePlatformPixmap::metric(PdmDevicePixelRatio) should return m_devicePixelRatio (for now the returned value is hardcoded to 1).
The commit cea58f4b77e1639e5671cf424544d4948fb8e9ef introduces PdmDevicePixelRatio metric.

I have added the following attachements (application output & gdb output).