Move SkAtomics.h to private.

tests/AtomicTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
-#include "SkAtomics.h"
+#include "../private/SkAtomics.h"
 #include "SkThreadUtils.h"
 #include "SkTypes.h"
 #include "Test.h"
 
 struct AddInfo {
     int32_t valueToAdd;
     int timesToAdd;
     unsigned int processorAffinity;
 };
 
@@ skipping 38 matching lines @@
 
     {
         SkAtomic<int> v {0};
         REPORTER_ASSERT(reporter, 0 == v.load());
         v = 10;
         REPORTER_ASSERT(reporter, 10 == v.load());
         int q = v;
         REPORTER_ASSERT(reporter, 10 == q);
     }
 }