Store constant variable initializers in elements.

pkg/compiler/lib/src/js_emitter/metadata_collector.dart

 // Copyright (c) 2013, 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.
 
 part of dart2js.js_emitter;
 
 /// Represents an entry's position in one of the global metadata arrays.
 ///
 /// [_rc] is used to count the number of references of the token in the
 /// ast for a program.
@@ skipping 195 matching lines @@
         }
       }
     }
 
     List<jsAst.DeferredNumber> defaultValues = <jsAst.DeferredNumber>[];
     for (ParameterElement element in signature.optionalParameters) {
       ParameterElement parameter =
           (targetParameterMap == null) ? element : targetParameterMap[element];
       ConstantValue constant = (parameter == null)
           ? null
-          : _backend.constants.getConstantValueForVariable(parameter);
+          : _backend.constants.getConstantValue(parameter.constant);
       jsAst.Expression expression = (constant == null)
           ? new jsAst.LiteralNull()
           : _emitter.constantReference(constant);
       defaultValues.add(_addGlobalMetadata(expression));
     }
     return defaultValues;
   }
 
   Map<ParameterElement, ParameterElement> mapRedirectingFactoryConstructorOptionalParameters(
       FunctionSignature source, FunctionSignature target) {
@@ skipping 191 matching lines @@
     if (token is _ForwardingMetadataEntry && !token.isBound) {
       _foundUnboundToken = true;
     }
   }
 
   bool findUnboundPlaceholders(jsAst.Node node) {
     node.accept(this);
     return _foundUnboundToken;
   }
 }