Store constant variable initializers in elements.

pkg/compiler/lib/src/js_backend/lookup_map_analysis.dart

 // Copyright (c) 2015, 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.
 
 /// Analysis to determine how to generate code for `LookupMap`s.
 library compiler.src.js_backend.lookup_map_analysis;
 
 import 'package:pub_semver/pub_semver.dart';
 
 import '../common.dart';
@@ skipping 137 matching lines @@
 
   /// Checks if the version of lookup_map is valid, and if so, enable this
   /// analysis during codegen.
   void onCodegenStart() {
     _inCodegen = true;
     if (lookupMapVersionVariable == null) return;
 
     // At this point, the lookupMapVersionVariable should be resolved and it's
     // constant value should be available.
     StringConstantValue value =
-        backend.constants.getConstantValueForVariable(lookupMapVersionVariable);
+        backend.constants.getConstantValue(lookupMapVersionVariable.constant);
     if (value == null) {
       reporter.reportInfo(lookupMapVersionVariable,
           MessageKind.UNRECOGNIZED_VERSION_OF_LOOKUP_MAP);
       return;
     }
 
     // TODO(sigmund): add proper version resolution using the pub_semver package
     // when we introduce the next version.
     Version version;
     try {
@@ skipping 260 matching lines @@
         original.fields[analysis.valueField] = keyValuePairs[1];
       }
     } else {
       original.fields[analysis.entriesField] =
           new ListConstantValue(listType, keyValuePairs);
     }
   }
 }
 
 final _validLookupMapVersionConstraint = new VersionConstraint.parse('^0.0.1');