Use unordered map hash on ConstructedConstantValue.

pkg/compiler/lib/src/util/util.dart

Index: pkg/compiler/lib/src/util/util.dart
diff --git a/pkg/compiler/lib/src/util/util.dart b/pkg/compiler/lib/src/util/util.dart
index 102ca9e1a021d5f80383ecd92d206943c61f5c5d..d9cc16c4c2e82df1f2c2d27398da36f3c6111c51 100644
--- a/pkg/compiler/lib/src/util/util.dart
+++ b/pkg/compiler/lib/src/util/util.dart
@@ -52,6 +52,16 @@ class Hashing {
     return h;
   }
 
+  /// Mix the bits of the hash codes of the unordered key/value from [map] with
+  /// [existing].
+  static int unorderedMapHash(Map map, [int existing = 0]) {
+    int h = 0;
+    for (var key in map.keys) {
+      h ^= objectHash(key, objectHash(map[key]));
+    }
+    return mixHashCodeBits(h, existing);
+  }
+
   /// Mix the bits of the key/value hash codes from [map] with [existing].
   static int mapHash(Map map, [int existing = 0]) {
     int h = existing;