Setup CCPR testing with GrMockContext

Beefs up the mock context to be able to support CCPR, sets up a
framework for testing CCPR with the mock context, and adds a new test.

Bug: skia:
Change-Id: If95f92726f7b1a7f52ad04ca8126551f58ea8032
Reviewed-on: https://skia-review.googlesource.com/67980
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Chris Dalton <csmartdalton@google.com>
11 files changed