Move GrResourceKey.h to include/private.

Change-Id: I87cebe1ba69afe3ff51e4f7b504e8caa0ade063f
Reviewed-on: https://skia-review.googlesource.com/c/179733
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>
3 files changed