DirectWrite to use aliased if ClearType is empty.

Some CJK fonts with some versions of DirectWrite return valid
data for bitmaps, but not for cleartype data.

For reference, two screenshots. M37 Stable and then with this patch:

http://imgur.com/9pf3rB9,EiTb6Li

See https://code.google.com/p/chromium/issues/detail?id=396624#c10 for
content of test html file.

R=eae@chromium.org, reed@google.com, shrikant@chromium.org, bungeman@chromium.org, cpu@chromium.org
BUG=chromium:407945

Review URL: https://codereview.chromium.org/504343007

Cherry-picked from b2f7fce9e034c3b6749e75a129e7836df3529706.
3 files changed