Clean up DirectWrite typeface cache matching.

The matching code was difficult to follow due to naming issues,
and performed some duplicate work which is not wanted.
This change will either fix the associated bug or make it possible
to track the cause.

CQ_EXTRA_TRYBOTS=tryserver.skia:Test-Win7-ShuttleA-HD2000-x86-Release-DirectWrite-Trybot

BUG=384529
R=reed@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/338923003