Audit all public methods of StyleResolver and remove the easy ones and add FIXMEs for removing others

We're very close to having StyleResolver just be a front-end to the style system
and not actually have any of the details of style resolution itself.

I suspect the next steps are moving all the match* functions out of StyleResolver
and creating a document-lifetime style caches object to hold things
like the RuleSets, the RuleFeatureSet, m_styleTree, etc.  Then we would be able
to more surgically nuke just the caches which need invalidating instead of
always deleting the whole StyleResolver object every time anything changes.

BUG=237268
R=dglazkov@chromium.org

Review URL: https://codereview.chromium.org/19517005

git-svn-id: svn://svn.chromium.org/blink/trunk@154435 bbb929c8-8fbe-4397-9dbb-9b2b20218538