Make header include guards great again

runtime/vm/bitfield.h

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // 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_BITFIELD_H_
-#define VM_BITFIELD_H_
+#ifndef RUNTIME_VM_BITFIELD_H_
+#define RUNTIME_VM_BITFIELD_H_
 
 namespace dart {
 
 static const uword kUwordOne = 1U;
 
 // BitField is a template for encoding and decoding a value of type T
 // inside a storage of type S.
 template<typename S, typename T, int position, int size>
 class BitField {
  public:
@@ skipping 43 matching lines @@
   // will be changed.
   static S update(T value, S original) {
     ASSERT(is_valid(value));
     return (static_cast<S>(value) << position) |
         (~mask_in_place() & original);
   }
 };
 
 }  // namespace dart
 
-#endif  // VM_BITFIELD_H_
+#endif  // RUNTIME_VM_BITFIELD_H_