Make header include guards great again

runtime/platform/hashmap.h

Index: runtime/platform/hashmap.h
diff --git a/runtime/platform/hashmap.h b/runtime/platform/hashmap.h
index 185c75f33b659ef23fcddac4a42428df77798122..1cd8a4a2331da44dfa5cd4ee233e5b499cfee24e 100644
--- a/runtime/platform/hashmap.h
+++ b/runtime/platform/hashmap.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 PLATFORM_HASHMAP_H_
-#define PLATFORM_HASHMAP_H_
+#ifndef RUNTIME_PLATFORM_HASHMAP_H_
+#define RUNTIME_PLATFORM_HASHMAP_H_
 
 #include "platform/globals.h"
 
@@ -105,4 +105,4 @@ class HashMap {
 
 }  // namespace dart
 
-#endif  // PLATFORM_HASHMAP_H_
+#endif  // RUNTIME_PLATFORM_HASHMAP_H_