Decouple RulesCacheDelegate from RulesRegistry

This is a prerequisite for declarative API support in <webview>. <webview>s should not cache their rules.

BUG=312461

Review URL: https://codereview.chromium.org/53273002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232651 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232651