Split atomic and mutex implementations and make inlinable.

src/ports/SkMutex_none.h

+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkMutex_none_DEFINED
+#define SkMutex_none_DEFINED
+
+/** Non-mutex mutex for uniprocessor systems. */
+
+struct SkBaseMutex {
+    void acquire() { }
+    void release() { }
+};
+
+class SkMutex : public SkBaseMutex {
+public:
+    SkMutex() { }
+    ~SkMutex() { }
+
+private:
+    SkMutex(const SkMutex&);
+    SkMutex& operator=(const SkMutex&);
+};
+
+// Using POD-style initialization prevents the generation of a static initializer.
+#define SK_DECLARE_STATIC_MUTEX(name) static SkBaseMutex name = { }
+
+// Special case used when the static mutex must be available globally.
+#define SK_DECLARE_GLOBAL_MUTEX(name) SkBaseMutex name = { }
+
+#endif