match getFontMetrics change in docs

Recent bookmaker changes make coordinating include
and bmh files a bit easier.

TBR=reed@google.com
NOTRY=true

Docs-Preview: https://skia.org/?cl=167547
Bug: skia:
Change-Id: I47d46cf639b13b152f79ef84a62d67da06ae8cf1
Reviewed-on: https://skia-review.googlesource.com/c/167547
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
Reviewed-by: Cary Clark <caryclark@skia.org>
2 files changed