Move Mutexy things to private.

include/core/SkSpinlock.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.
- */
-
-// This file is not part of the public Skia API.
-
-#ifndef SkSpinlock_DEFINED
-#define SkSpinlock_DEFINED
-
-#include "../private/SkAtomics.h"
-
-#define SK_DECLARE_STATIC_SPINLOCK(name) namespace {} static SkPODSpinlock name
-
-// This class has no constructor and must be zero-initialized (the macro above does this).
-class SK_API SkPODSpinlock {
-public:
-    void acquire() {
-        // To act as a mutex, we need an acquire barrier if we take the lock.
-        if (sk_atomic_exchange(&fLocked, true, sk_memory_order_acquire)) {
-            // Lock was contended.  Fall back to an out-of-line spin loop.
-            this->contendedAcquire();
-        }
-    }
-
-    void release() {
-        // To act as a mutex, we need a release barrier.
-        sk_atomic_store(&fLocked, false, sk_memory_order_release);
-    }
-
-private:
-    void contendedAcquire();
-    bool fLocked;
-};
-
-// For non-global-static use cases, this is normally what you want.
-class SkSpinlock : public SkPODSpinlock {
-public:
-    SkSpinlock() { this->release(); }
-};
-
-#endif//SkSpinlock_DEFINED