Automatically choose device pixel ratio
Automatically choose device pixel ratio

Change-Id: Ic595ee0f45b7d3ec22b4c4086c0c6785b41c21f4
Task-number: QTCREATORBUG-11179
Reviewed-by: Friedemann Kleint <1b9f2592239daaec4856ccc1cfb4d2d55b35fb71@theqtcompany.com>
Reviewed-by: Eike Ziller <c142da16c73a95a82d35191bcc55b22835617128@theqtcompany.com>

martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator,martyone/sailfish-qtcreator,xianian/qt-creator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,martyone/sailfish-qtcreator,xianian/qt-creator,xianian/qt-creator