Reapply "Improve hashCode for closure objects" with fixes.

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 RUNTIME_VM_SYMBOLS_H_
 #define RUNTIME_VM_SYMBOLS_H_
 
 #include "vm/growable_array.h"
 #include "vm/object.h"
 #include "vm/snapshot_ids.h"
@@ skipping 372 matching lines @@
   V(_LocalCombinatorMirror, "_LocalCombinatorMirror")                          \
   V(_LocalMethodMirror, "_LocalMethodMirror")                                  \
   V(_LocalVariableMirror, "_LocalVariableMirror")                              \
   V(_LocalParameterMirror, "_LocalParameterMirror")                            \
   V(_LocalIsolateMirror, "_LocalIsolateMirror")                                \
   V(_LocalMirrorSystem, "_LocalMirrorSystem")                                  \
   V(_LocalTypedefMirror, "_LocalTypedefMirror")                                \
   V(_LocalTypeVariableMirror, "_LocalTypeVariableMirror")                      \
   V(_SourceLocation, "_SourceLocation")                                        \
   V(hashCode, "get:hashCode")                                                  \
+  V(identityHashCode, "identityHashCode")                                      \
   V(OptimizedOut, "<optimized out>")                                           \
   V(NotInitialized, "<not initialized>")                                       \
   V(NotNamed, "<not named>")                                                   \
   V(TempParam, ":temp_param")                                                  \
   V(_UserTag, "_UserTag")                                                      \
   V(Default, "Default")                                                        \
   V(ClassID, "ClassID")                                                        \
   V(DartIsVM, "dart.isVM")                                                     \
   V(stack, ":stack")                                                           \
   V(stack_pointer, ":stack_pointer")                                           \
@@ skipping 292 matching lines @@
   friend class Serializer;
   friend class Deserializer;
   friend class ApiMessageReader;
 
   DISALLOW_COPY_AND_ASSIGN(Symbols);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_SYMBOLS_H_