Make header include guards great again

runtime/vm/tags.h

Index: runtime/vm/tags.h
diff --git a/runtime/vm/tags.h b/runtime/vm/tags.h
index 8c6ef65d3c9704d6ec54e19b35feeb46c27e7e3c..c6a0230ccc79a0507ac924a76c3308d23ac6f571 100644
--- a/runtime/vm/tags.h
+++ b/runtime/vm/tags.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_TAGS_H_
-#define VM_TAGS_H_
+#ifndef RUNTIME_VM_TAGS_H_
+#define RUNTIME_VM_TAGS_H_
 
 #include "vm/allocation.h"
 
@@ -123,4 +123,4 @@ class UserTags : public AllStatic {
 
 }  // namespace dart
 
-#endif  // VM_TAGS_H_
+#endif  // RUNTIME_VM_TAGS_H_