Do not try to write ContextScope into a snapshot.

vm/snapshot.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_SNAPSHOT_H_
 #define VM_SNAPSHOT_H_
 
 #include "platform/assert.h"
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
@@ skipping 483 matching lines @@
   Snapshot::Kind kind_;
   ObjectStore* object_store_;  // Object store for common classes.
   ClassTable* class_table_;  // Class table for the class index to class lookup.
   GrowableArray<ForwardObjectNode*> forward_list_;
   Exceptions::ExceptionType exception_type_;  // Exception type.
   const char* exception_msg_;  // Message associated with exception.
   LanguageError& error_;  // Error handle.
 
   friend class RawArray;
   friend class RawClass;
+  friend class RawClosureData;
   friend class RawGrowableObjectArray;
   friend class RawImmutableArray;
   friend class RawJSRegExp;
   friend class RawLibrary;
   friend class RawLiteralToken;
   friend class RawScript;
   friend class RawTokenStream;
   friend class RawTypeArguments;
   friend class SnapshotWriterVisitor;
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriter);
@@ skipping 72 matching lines @@
  private:
   SnapshotWriter* writer_;
   bool as_references_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotWriterVisitor);
 };
 
 }  // namespace dart
 
 #endif  // VM_SNAPSHOT_H_