Make header include guards great again

runtime/vm/atomic.h

Index: runtime/vm/atomic.h
diff --git a/runtime/vm/atomic.h b/runtime/vm/atomic.h
index e16eee18a5213234cdd220709c8637a93529ad5d..75d0b846fa746ff1e277c9256c5aa521ce7fba91 100644
--- a/runtime/vm/atomic.h
+++ b/runtime/vm/atomic.h
@@ -2,8 +2,8 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-#ifndef VM_ATOMIC_H_
-#define VM_ATOMIC_H_
+#ifndef RUNTIME_VM_ATOMIC_H_
+#define RUNTIME_VM_ATOMIC_H_
 
 #include "platform/globals.h"
 
@@ -86,4 +86,4 @@ class AtomicOperations : public AllStatic {
 #error Unknown target os.
 #endif
 
-#endif  // VM_ATOMIC_H_
+#endif  // RUNTIME_VM_ATOMIC_H_