Remove unused parameter to RenderLayerCompositor::setCompositingLayersNeedRebuild

TBR=esprehn@chromium.org

Review URL: https://codereview.chromium.org/185273002

git-svn-id: svn://svn.chromium.org/blink/trunk@168248 bbb929c8-8fbe-4397-9dbb-9b2b20218538