Remove Node::parentNodeForRenderingAndStyle and switch to parentRenderStyle

parentNodeForRenderingAndStyle() was a complicated way of doing NodeRenderingTraversal::parent.
This switches to that, but more importantly it makes us stop calling into the
ComposedShadowTreeWalker::traverseParent twice during recalcStyle which was crazy since that's
tons of code to do twice just for a ternary.

R=eseidel@chromium.org,ojan@chromium.org,eae@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19962004

git-svn-id: svn://svn.chromium.org/blink/trunk@154682 bbb929c8-8fbe-4397-9dbb-9b2b20218538