Store constant variable initializers in elements.

pkg/compiler/lib/src/js_emitter/program_builder/program_builder.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.js_emitter.program_builder;
 
 import '../../closure.dart' show ClosureFieldElement;
 import '../../common.dart';
 import '../../common/names.dart' show Names, Selectors;
 import '../../compiler.dart' show Compiler;
@@ skipping 672 matching lines @@
       return _buildStaticMethod(element);
     }
   }
 
   /* Map | List */ _computeParameterDefaultValues(FunctionSignature signature) {
     var /* Map | List */ optionalParameterDefaultValues;
     if (signature.optionalParametersAreNamed) {
       optionalParameterDefaultValues = new Map<String, ConstantValue>();
       signature.forEachOptionalParameter((ParameterElement parameter) {
         ConstantValue def =
-            backend.constants.getConstantValueForVariable(parameter);
+            backend.constants.getConstantValue(parameter.constant);
         optionalParameterDefaultValues[parameter.name] = def;
       });
     } else {
       optionalParameterDefaultValues = <ConstantValue>[];
       signature.forEachOptionalParameter((ParameterElement parameter) {
         ConstantValue def =
-            backend.constants.getConstantValueForVariable(parameter);
+            backend.constants.getConstantValue(parameter.constant);
         optionalParameterDefaultValues.add(def);
       });
     }
     return optionalParameterDefaultValues;
   }
 
   DartMethod _buildMethod(MethodElement element) {
     js.Name name = namer.methodPropertyName(element);
     js.Expression code = backend.generatedCode[element];
 
@@ skipping 264 matching lines @@
       Constant constant = new Constant(name, holder, constantValue);
       _constants[constantValue] = constant;
     }
   }
 
   Holder _registerStaticStateHolder() {
     return _registry.registerHolder(namer.staticStateHolder,
         isStaticStateHolder: true);
   }
 }