Revert "Revert "SkTypes: extract SkTo""

This reverts commit fdcfb8b7c23fbf18f872d2c31d27978235033876.

> Original change's description:
> > SkTypes: extract SkTo
> >
> > Change-Id: I8de790d5013db2105ad885fa2683303d7c250b09
> > Reviewed-on: https://skia-review.googlesource.com/133620
> > Reviewed-by: Mike Klein <mtklein@google.com>

Change-Id: Ida74fbc5c21248a724a5edbf9fae18a33bcb23aa
Reviewed-on: https://skia-review.googlesource.com/134506
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Hal Canary <halcanary@google.com>
diff --git a/include/gpu/GrResourceKey.h b/include/gpu/GrResourceKey.h
index 0240387..90b84d7 100644
--- a/include/gpu/GrResourceKey.h
+++ b/include/gpu/GrResourceKey.h
@@ -1,4 +1,3 @@
-
 /*
  * Copyright 2014 Google Inc.
  *
@@ -11,6 +10,7 @@
 
 #include "../private/SkOnce.h"
 #include "../private/SkTemplates.h"
+#include "../private/SkTo.h"
 #include "GrTypes.h"
 #include "SkData.h"
 #include "SkString.h"