RenderListMarker shouldn't use bloatedCharacters()

Thee's no need to bloat characters to feed them to a TextRun. We now support 8
bit text runs.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/19241003

git-svn-id: svn://svn.chromium.org/blink/trunk@154262 bbb929c8-8fbe-4397-9dbb-9b2b20218538