When showing the ntp page login header that show the connected status of
the profile, don't call signin::ShoudShowPromo() to determine if it should
be displayed or not.  It should only be shown if the user is allowed to
sign in (and this is not chromeos).

BUG=289339

Review URL: https://codereview.chromium.org/23591039

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225539 0039d316-1c4b-4281-b951-d872f2087c98
Rename "disable-legacy-encrytped-media" flag to "disable-prefixed-encrypted-media".

The new name better reflects what this flag is doing.

TBR=jochen@chromium.org,davemoore@chromium.org

Review URL: https://codereview.chromium.org/24228004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225540 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225540