win dw: Fallback to aliased if ClearType 'succeeds' but returns empty

win dw: Fallback to aliased if ClearType 'succeeds' but returns empty

This appears to happen for some CJK fonts where DW only returns valid
data for bitmaps, not for cleartype data.

This has an artifact (of course) which is that during the run where this
failure case is encountered, cleartype will appear incongrously next to
aliased, which looks poor. So, we'll need to fallback at a higher level.

However, for M37, having something visible is more desirable than
rendering blank space for characters.

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=shrikant@chromium.org,bungeman@chromium.org,eae@chromium.org,cpu@chromium.org
BUG=chromium:407945

[scottmg, 2014-08-27 20:12:51]

scottmg@chromium.org changed reviewers:
+ shrikant@chromium.org
- skrikant@chromium.org

[scottmg, 2014-08-27 20:13:24]

Oops, can't speel Shrikant's name apparently. :/

[scottmg, 2014-08-27 20:48:20]

On 2014/08/27 20:13:24, scottmg wrote:
> Oops, can't speel Shrikant's name apparently. :/

Sorry, moved here to be Skia patch instead of on to chrome mirror:
https://codereview.chromium.org/510563003/

[eae, 2014-08-27 21:13:19]

General approach seems fine, not sure a goto statement is the right
implementation though but I'll leave that up to the Skia reviewers.