RenderObject bits setters don't use the default parameter

Thus we can remove them. It shouldn't matter for the compiler
but it should make the caller more explicit, instead of relying
on the confusing default parameter.

Review URL: https://codereview.chromium.org/87083002

git-svn-id: svn://svn.chromium.org/blink/trunk@162671 bbb929c8-8fbe-4397-9dbb-9b2b20218538