Fix ConstrastEffect in qml-compositor
Fix ConstrastEffect in qml-compositor

Specify precision to make the shader working.

Change-Id: I055fe47e1073403dc981274236fa82e091e0eca4
Reviewed-by: Jørgen Lind <6105bb7d7ebdd613cef5835c4a38d29949bd95ac@digia.com>
Reviewed-by: Andy Nichols <3d1e63b963f99f97839545621c6a9a8e2b2ab8fd@digia.com>

ntanibata/qtwayland,locusf/qtwayland-1,Tofee/qtwayland,ntanibata/qtwayland,locusf/qtwayland-1,Tofee/qtwayland,Tofee/qtwayland,locusf/qtwayland-1,locusf/qtwayland-1,ntanibata/qtwayland