Ignore text-shadow when printing.

This undoes an accidental change in behaviour earlier on. It's not clear
what the "right" behaviour here is, but this is the simplest way to
avoid the regression in question.

BUG=258321

Review URL: https://chromiumcodereview.appspot.com/19424002

git-svn-id: svn://svn.chromium.org/blink/trunk@154505 bbb929c8-8fbe-4397-9dbb-9b2b20218538