Use normal equality for const maps.

sdk/lib/_internal/lib/constant_map.dart

Index: sdk/lib/_internal/lib/constant_map.dart
diff --git a/sdk/lib/_internal/lib/constant_map.dart b/sdk/lib/_internal/lib/constant_map.dart
index f13f30911b03c4078dc9c18a24bb92a1ee437742..e3326371c9bb3286c817752f19d6bfad986ca75c 100644
--- a/sdk/lib/_internal/lib/constant_map.dart
+++ b/sdk/lib/_internal/lib/constant_map.dart
@@ -103,8 +103,7 @@ class GeneralConstantMap<K, V> extends ConstantMap<K, V> {
   // have not been defined when constants are created.
   Map<K, V> _getMap() {
     if (JS('bool', r'!this.$map')) {
-      Map backingMap =
-          new LinkedHashMap<K, V>(equals: identical, hashCode: objectHashCode);
+      Map backingMap = new Map<K, V>();
       JS('', r'this.$map = #', fillLiteralMap(_jsData, backingMap));

[Lasse Reichstein Nielsen, 2014/02/27 08:15:34]

The spec is silent on how constant maps work, but the constant keys objects must
not implement equals, or they must be String or int. 
So, in dart2js where strings are identical if equal, this should change nothing,
correct?

Except if the objects override hashCode in an incompatible way, but then they
deserve what they get.

     }
     return JS('Map', r'this.$map');