Revert "Remove Registry from registerMetadataConstant" and "Serialize metadata"

pkg/compiler/lib/src/cps_ir/cps_ir_nodes_sexpr.dart

 // Copyright (c) 2014, 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.
 
 library dart2js.ir_nodes_sexpr;
 
 import '../constants/values.dart';
 import '../util/util.dart';
 import 'cps_ir_nodes.dart';
 import '../universe/call_structure.dart' show CallStructure;
@@ skipping 457 matching lines @@
   }
 
   String visitFunction(FunctionConstantValue constant, _) {
     return '(Function "${constant.toDartText()}")';
   }
 
   String visitNull(NullConstantValue constant, _) {
     return '(Null)';
   }
 
-  String visitNonConstant(NonConstantValue constant, _) {
-    return '(NonConstant)';
-  }
-
   String visitInt(IntConstantValue constant, _) {
     return '(Int ${constant.toDartText()})';
   }
 
   String visitDouble(DoubleConstantValue constant, _) {
     return '(Double ${constant.toDartText()})';
   }
 
   String visitBool(BoolConstantValue constant, _) {
     return '(Bool ${constant.toDartText()})';
@@ skipping 73 matching lines @@
   void setReturnContinuation(Continuation node) {
     assert(!_names.containsKey(node) || _names[node] == 'return');
     _names[node] = 'return';
   }
 
   String getName(Node node) {
     if (!_names.containsKey(node)) return 'MISSING_NAME';
     return _names[node];
   }
 }