Always show the Chrome Frame turndown prompt.

This change removes the dismiss button (reverting r213426 and r213521)
as well as the reshow delta (effectively making the delta 0).

BUG=none

Review URL: https://codereview.chromium.org/52583002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232064 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232064