Fix rendering of user-select: none selections

Since r157239 (and possible earlier since that was a revert) user-
select: none selections would sometimes be painted with a transparent
foreground color. This is clearly not desireable.

BUG=288691
R=leviw@chromium.org
TEST=LayoutTests/fast/css/user-select-none.html

Review URL: https://chromiumcodereview.appspot.com/23983027

git-svn-id: svn://svn.chromium.org/blink/trunk@157645 bbb929c8-8fbe-4397-9dbb-9b2b20218538