- Add functionality to morph a string into an external string

vm/raw_object.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_RAW_OBJECT_H_
 #define VM_RAW_OBJECT_H_
 
 #include "platform/assert.h"
 #include "vm/globals.h"
 #include "vm/token.h"
@@ skipping 1186 matching lines @@
   }
   RawObject** to(intptr_t length) {
     return reinterpret_cast<RawObject**>(&ptr()->data()[length - 1]);
   }
 
   friend class RawCode;
   friend class RawImmutableArray;
   friend class SnapshotReader;
   friend class GrowableObjectArray;
   friend class Object;
+  friend class String;
 };
 
 
 class RawImmutableArray : public RawArray {
   RAW_HEAP_OBJECT_IMPLEMENTATION(ImmutableArray);
 
   friend class SnapshotReader;
 };
 
 
@@ skipping 393 matching lines @@
          kExternalUint64ArrayCid == kExternalInt8ArrayCid + 7 &&
          kExternalFloat32ArrayCid == kExternalInt8ArrayCid + 8 &&
          kExternalFloat64ArrayCid == kExternalInt8ArrayCid + 9 &&
          kStacktraceCid == kExternalInt8ArrayCid + 10);
   return (index >= kExternalInt8ArrayCid && index <= kExternalFloat64ArrayCid);
 }
 
 }  // namespace dart
 
 #endif  // VM_RAW_OBJECT_H_