computeCanUseSimpleFontCodePath shouldn't use bloatedCharacters

We already know that the RenderText isn't 8 bit at this program point.

R=eseidel
BUG=254708

Review URL: https://chromiumcodereview.appspot.com/19610005

git-svn-id: svn://svn.chromium.org/blink/trunk@154438 bbb929c8-8fbe-4397-9dbb-9b2b20218538