Disable incognito link if parental control is on
The CL disables the incognito link on the gaia page if parental control is on. It adds a cached version for windows parental control check so that it may be accessed from IO thread. A similar CL for thread-safe android parental control check is under review at https://chrome-internal-review.googlesource.com/#/c/166265/.
BUG=383682
Review URL: https://codereview.chromium.org/
336213005
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278848 0039d316-1c4b-4281-b951-d872f2087c98