Set the kMultiMaster_FontFlag in DirectWrite.

DirectWrite can now produce system font typefaces which are variations,
so mark these as multiple masters so printing knows what to do.

BUG=chromium:697916

Change-Id: Idf09ebba3c7002a09ff2e4a2dbae13dbce4e79d4
Reviewed-on: https://skia-review.googlesource.com/12101
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Hal Canary <halcanary@google.com>
2 files changed