Encoding API: Use 'windows-1252' as name for 'us-ascii'  'iso-8859-1'

Aliasing is done at the API level, since Blink intentionally maintains
differently named codec instances for these, even though the same
codec is actually used.

R=kbr@chromium.org,jshin@chromium.org
BUG=277027,277030

Review URL: https://chromiumcodereview.appspot.com/23455007

git-svn-id: svn://svn.chromium.org/blink/trunk@156863 bbb929c8-8fbe-4397-9dbb-9b2b20218538