Revert of skstd -> std for unique_ptr

include/core/SkRefCnt.h

Index: include/core/SkRefCnt.h
diff --git a/include/core/SkRefCnt.h b/include/core/SkRefCnt.h
index 1033bccc889b72783bf357233f1a625e9098d265..0e8d857722d2678d8620fe923267fff82b7e197e 100644
--- a/include/core/SkRefCnt.h
+++ b/include/core/SkRefCnt.h
@@ -9,8 +9,8 @@
 #define SkRefCnt_DEFINED
 
 #include "../private/SkAtomics.h"
+#include "../private/SkUniquePtr.h"
 #include "SkTypes.h"
-#include <memory>
 
 /** \class SkRefCntBase
 
@@ -185,9 +185,9 @@
 /**
  *  Utility class that simply unref's its argument in the destructor.
  */
-template <typename T> class SkAutoTUnref : public std::unique_ptr<T, SkTUnref<T>> {
-public:
-    explicit SkAutoTUnref(T* obj = nullptr) : std::unique_ptr<T, SkTUnref<T>>(obj) {}
+template <typename T> class SkAutoTUnref : public skstd::unique_ptr<T, SkTUnref<T>> {
+public:
+    explicit SkAutoTUnref(T* obj = nullptr) : skstd::unique_ptr<T, SkTUnref<T>>(obj) {}
 
     T* detach() { return this->release(); }
     operator T*() const { return this->get(); }