Remove Gr*Gpu includes from header files.

Some general cleanup to try to keep use of the backend gpu class in cpps.

Bug: skia:
Change-Id: I1a28e0e5c2e55562b3fff56c284c3405b5b6d8bc
Reviewed-on: https://skia-review.googlesource.com/20057
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Greg Daniel <egdaniel@google.com>
10 files changed