Add skstd::unique_ptr and use it.

include/private/SkUtility.h

+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkUtility_DEFINED
+#define SkUtility_DEFINED
+
+#include "SkTLogic.h"
+
+namespace skstd {
+
+template <typename T> inline remove_reference_t<T>&& move(T&& t) {
+  return static_cast<remove_reference_t<T>&&>(t);
+}
+
+template <typename T> inline T&& forward(remove_reference_t<T>& t) /*noexcept*/ {
+    return static_cast<T&&>(t);
+}
+template <typename T> inline T&& forward(remove_reference_t<T>&& t) /*noexcept*/ {
+    static_assert(!is_lvalue_reference<T>::value,
+                  "Forwarding an rvalue reference as an lvalue reference is not allowed.");
+    return static_cast<T&&>(t);
+}
+
+template <typename T> add_rvalue_reference_t<T> declval();
+
+}  // namespace skstd
+
+#endif