Start adding vm/cc tests for rewind functionality.

runtime/vm/dart_api_message.cc

 // 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.
 
 #include "vm/dart_api_message.h"
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
 #include "vm/symbols.h"
 #include "vm/unicode.h"
 
@@ skipping 1282 matching lines @@
       break;
     }
     case Dart_CObject_kCapability: {
       WriteInlinedHeader(object);
       WriteIndexedObject(kCapabilityCid);
       WriteTags(0);
       Write<uint64_t>(object->value.as_capability.id);
       break;
     }
     default:
-      UNREACHABLE();
+      FATAL1("Unexpected Dart_CObject_Type %d\n", type);
   }
 
   return true;
 }
 
 
 bool ApiMessageWriter::WriteCMessage(Dart_CObject* object) {
   bool success = WriteCObject(object);
   if (!success) {
     UnmarkAllCObjects(object);
     return false;
   }
   // Write out all objects that were added to the forward list and have
   // not been serialized yet. These would typically be fields of arrays.
   // NOTE: The forward list might grow as we process the list.
   for (intptr_t i = 0; i < forward_id_; i++) {
     success = WriteForwardedCObject(forward_list_[i]);
     if (!success) {
       UnmarkAllCObjects(object);
       return false;
     }
   }
   UnmarkAllCObjects(object);
   return true;
 }
 
 }  // namespace dart