Make header include guards great again

runtime/vm/datastream.h

 // Copyright (c) 2012, 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_DATASTREAM_H_
-#define VM_DATASTREAM_H_
+#ifndef RUNTIME_VM_DATASTREAM_H_
+#define RUNTIME_VM_DATASTREAM_H_
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/allocation.h"
 #include "vm/exceptions.h"
 #include "vm/globals.h"
 #include "vm/os.h"
 
 namespace dart {
 
@@ skipping 454 matching lines @@
   uint8_t* current_;
   intptr_t current_size_;
   ReAlloc alloc_;
   intptr_t initial_size_;
 
   DISALLOW_COPY_AND_ASSIGN(WriteStream);
 };
 
 }  // namespace dart
 
-#endif  // VM_DATASTREAM_H_
+#endif  // RUNTIME_VM_DATASTREAM_H_