Remove StyleResolverScope, and just create new StyleResolverStates in each scope.

To reduce the amount of interface churn from this CL, I've turned the
m_state field in StyleResolver into a pointer to the current State.
The next step is to thread this through the function arguments.

Review URL: https://chromiumcodereview.appspot.com/19688007

git-svn-id: svn://svn.chromium.org/blink/trunk@154549 bbb929c8-8fbe-4397-9dbb-9b2b20218538