Reviewed by Dan Bernstein.

        Setting zero size on a container of a video element doesn't hide the controller
        https://bugs.webkit.org/show_bug.cgi?id=30031

        Fix a logic error in enclosingCompositingLayer() when mixing normal flow and
        positioned layers. This resulted in enclosingCompositingLayer() giving back a different
        answer to the logic used to actually parent compositing layers, so layer positions
        and layer hierarchy would be out of agreement.

        Test: compositing/geometry/clipped-video-controller.html

        * rendering/RenderLayer.cpp:
        (WebCore::compositingContainer):
        (WebCore::RenderLayer::enclosingCompositingLayer):
        * rendering/RenderLayerCompositor.cpp:
        (WebCore::RenderLayerCompositor::setCompositingParent):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@49052 268f45cc-cd09-0410-ab3c-d52691b4dbfc