Make List an abstract class.

runtime/vm/symbols.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_SYMBOLS_H_
 #define VM_SYMBOLS_H_
 
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
 
@@ skipping 24 matching lines @@
   V(ClosureParameter, ":closure")                                              \
   V(PhaseParameter, ":phase")                                                  \
   V(TypeArgumentsParameter, ":type_arguments")                                 \
   V(AssertionError, "AssertionErrorImplementation")                            \
   V(TypeError, "TypeErrorImplementation")                                      \
   V(FallThroughError, "FallThroughErrorImplementation")                        \
   V(AbstractClassInstantiationError,                                           \
     "AbstractClassInstantiationErrorImplementation")                           \
   V(NoSuchMethodError, "NoSuchMethodErrorImplementation")                      \
   V(ThrowNew, "_throwNew")                                                     \
+  V(List, "List")                                                              \
   V(ListLiteralFactory, "List._fromLiteral")                                   \
-  V(ListImplementation, "_ListImpl")                                           \
   V(ListFactory, "List.")                                                      \
   V(MapImplementation, "_HashMapImpl")                                         \
   V(MapLiteralFactory, "Map._fromLiteral")                                     \
   V(ImmutableMap, "ImmutableMap")                                              \
   V(ImmutableMapConstructor, "ImmutableMap._create")                           \
   V(StringBase, "_StringBase")                                                 \
   V(Interpolate, "_interpolate")                                               \
   V(GetIterator, "iterator")                                                   \
   V(NoSuchMethod, "noSuchMethod")                                              \
   V(SavedArgDescVarPrefix, ":saved_args_desc_var")                             \
@@ skipping 175 matching lines @@
   friend class SnapshotReader;
   friend class SnapshotWriter;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // VM_SYMBOLS_H_