[SkTextBlob] Custom run font record

Instead of using a full-blown SkPaint to store run font info, use a
custom structure.

This saves 96 bytes / run on 64bit platforms.

R=reed@google.com,mtklein@google.com,joshualitt@google.com

Review URL: https://codereview.chromium.org/1070943002
2 files changed