Move GrSwizzle.h from include/private to src/gpu.

Change-Id: I2d992404f540c7f8a1cd5ff633148d92ec50d4fa
Reviewed-on: https://skia-review.googlesource.com/135860
Commit-Queue: Brian Salomon <bsalomon@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Auto-Submit: Brian Salomon <bsalomon@google.com>

gn/gpu.gni

@@ -40,7 +40,6 @@ skia_gpu_sources = [
   "$_include/private/GrRenderTargetProxy.h",
   "$_include/private/GrSurfaceProxy.h",
   "$_include/private/GrSurfaceProxyRef.h",
-  "$_include/private/GrSwizzle.h",
   "$_include/private/GrTextureProxy.h",
   "$_include/private/GrTypesPriv.h",
 
@@ -190,6 +189,7 @@ skia_gpu_sources = [
   "$_src/gpu/GrSurfaceContextPriv.h",
   "$_src/gpu/GrSurfaceProxyPriv.h",
   "$_src/gpu/GrSurfaceProxyRef.cpp",
+  "$_src/gpu/GrSwizzle.h",
   "$_src/gpu/GrTessellator.cpp",
   "$_src/gpu/GrTessellator.h",
   "$_src/gpu/GrTextureOpList.cpp",

src/gpu/GrShaderCaps.h

@@ -8,7 +8,7 @@
 #ifndef GrShaderCaps_DEFINED
 #define GrShaderCaps_DEFINED
 
-#include "../private/GrSwizzle.h"
+#include "GrSwizzle.h"
 #include "GrTypesPriv.h"
 #include "SkRefCnt.h"
 #include "glsl/GrGLSL.h"