Rules Registry Optimization: Don't fill in rules pulled from storage

As a follow-up to a previous refactoring, http://crrev.com/49693003, this
CL avoids initializing rules that are pulled from storage as they are already
initialized. This should address concerns about a potential performance regression.

BUG=312461

Review URL: https://codereview.chromium.org/61763021

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235203 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235203