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>
diff --git a/gn/gpu.gni b/gn/gpu.gni
index c857cdc..2c91477 100644
--- a/gn/gpu.gni
+++ b/gn/gpu.gni
@@ -18,7 +18,6 @@
   "$_include/gpu/GrDriverBugWorkarounds.h",
   "$_include/gpu/GrGpuResource.h",
   "$_include/gpu/GrRenderTarget.h",
-  "$_include/gpu/GrResourceKey.h",
   "$_include/gpu/GrSurface.h",
   "$_include/gpu/GrTexture.h",
   "$_include/gpu/GrSamplerState.h",
@@ -40,6 +39,7 @@
   "$_include/private/GrProxyRef.h",
   "$_include/private/GrSingleOwner.h",
   "$_include/private/GrRenderTargetProxy.h",
+  "$_include/private/GrResourceKey.h",
   "$_include/private/GrSurfaceProxy.h",
   "$_include/private/GrTextureProxy.h",
   "$_include/private/GrTypesPriv.h",