Translate: Disable offer-to-translate checkboxes when Translate is disabled

When the user disables Translate feature, "Offer to translate..." checkboxes should be disabled and unchecked because the checking state doesn't make sense in this case.

BUG=298321

Review URL: https://codereview.chromium.org/24983004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@226207 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 226207