Create test isolates using a snapshot, this ensures that we do not depend

runtime/vm/raw_object_snapshot.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/bigint_operations.h"
 #include "vm/object.h"
 #include "vm/object_store.h"
 #include "vm/snapshot.h"
 #include "vm/symbols.h"
 #include "vm/visitor.h"
@@ skipping 1029 matching lines @@
 RawLibrary* Library::ReadFrom(SnapshotReader* reader,
                               intptr_t object_id,
                               intptr_t tags,
                               Snapshot::Kind kind) {
   ASSERT(reader != NULL);
   ASSERT(kind != Snapshot::kMessage);
 
   Library& library = Library::ZoneHandle(reader->isolate(), Library::null());
   reader->AddBackRef(object_id, &library, kIsDeserialized);
 
-  if (RawObject::IsCreatedFromSnapshot(tags)) {
+  if ((kind == Snapshot::kScript) && RawObject::IsCreatedFromSnapshot(tags)) {
     ASSERT(kind != Snapshot::kFull);
     // Lookup the object as it should already exist in the heap.
     *reader->StringHandle() ^= reader->ReadObjectImpl();
     library = Library::LookupLibrary(*reader->StringHandle());
   } else {
     // Allocate library object.
     library = NEW_OBJECT(Library);
 
     // Set the object tags.
     library.set_tags(tags);
@@ skipping 1579 matching lines @@
   // Write out the class and tags information.
   writer->WriteIndexedObject(kWeakPropertyCid);
   writer->WriteIntptrValue(writer->GetObjectTags(this));
 
   // Write out all the other fields.
   writer->Write<RawObject*>(ptr()->key_);
   writer->Write<RawObject*>(ptr()->value_);
 }
 
 }  // namespace dart