Outline SkSpinlock::acquire().

src/core/SkSpinlock.cpp

Index: src/core/SkSpinlock.cpp
diff --git a/src/core/SkSpinlock.cpp b/src/core/SkSpinlock.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..0f764278df08839c30b13c830cc6fa88338e3074
--- /dev/null
+++ b/src/core/SkSpinlock.cpp
@@ -0,0 +1,13 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkSpinlock.h"
+
+void SkPODSpinlock::contendedAcquire() {
+    // To act as a mutex, we need an acquire barrier when we take the lock.
+    while(sk_atomic_exchange(&fLocked, true, sk_memory_order_acquire)) { /*spin*/ }
+}