Add SkBarriers to ports.

src/ports/SkBarriers_arm.h

Index: src/ports/SkBarriers_arm.h
diff --git a/src/ports/SkBarriers_arm.h b/src/ports/SkBarriers_arm.h
new file mode 100644
index 0000000000000000000000000000000000000000..9161cddebcffb1ed0611197066351cc9c80b2db3
--- /dev/null
+++ b/src/ports/SkBarriers_arm.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkBarriers_arm_DEFINED
+#define SkBarriers_arm_DEFINED
+
+static inline void sk_compiler_barrier() { asm volatile("" : : : "memory"); }
+
+template <typename T>
+T sk_acquire_load(T* ptr) {
+    T val = *ptr;
+    __sync_synchronize();  // Issue a full barrier, which is an overkill acquire barrier.
+    return val;
+}
+
+template <typename T>
+void sk_release_store(T* ptr, T val) {
+    __sync_synchronize();  // Issue a full barrier, which is an overkill release barrier.
+    *ptr = val;
+}
+
+#endif//SkBarriers_x86_DEFINED