Split SkFontHost_win_dw.

Split SkFontHost_win_dw into FontMgr, Typeface, and ScalerContext.
This makes working on these files easier, and moves away from the legacy
FontHost naming.

R=reed@google.com

Author: bungeman@google.com

Review URL: https://codereview.chromium.org/314193002
7 files changed