Enforce SafetyMode for YouTube if prefs::kForceSafeSearch is on, by modifying (or adding) YouTube's PrefCookie in the HTTP header.
This is essentially a followup to https://codereview.chromium.org/
11186002/
Note: This is a fixed reland of crrev.com/282546 / https://codereview.chromium.org/
354183002/ which was reverted due to a bug in ParseRequestCookieLine.
TBRing since it has already been reviewed in the first try.
TBR=erikwright@chromium.org
BUG=344815
Review URL: https://codereview.chromium.org/
388823002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@284687 0039d316-1c4b-4281-b951-d872f2087c98