move SkTPin to include/private

Change-Id: Ib0dc823d331a7cddc5da1d1be83136ce803a7871
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/327783
Commit-Queue: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>
diff --git a/src/utils/SkShadowUtils.cpp b/src/utils/SkShadowUtils.cpp
index 10e1319..615b5d7 100644
--- a/src/utils/SkShadowUtils.cpp
+++ b/src/utils/SkShadowUtils.cpp
@@ -15,6 +15,7 @@
 #include "include/core/SkVertices.h"
 #include "include/private/SkColorData.h"
 #include "include/private/SkIDChangeListener.h"
+#include "include/private/SkTPin.h"
 #include "include/utils/SkRandom.h"
 #include "src/core/SkBlurMask.h"
 #include "src/core/SkColorFilterBase.h"