Share the JavaScript based LinkedHashMap implementation between constant maps and the LinkedHashMap…

sdk/lib/_internal/compiler/js_lib/constant_map.dart

Index: sdk/lib/_internal/compiler/js_lib/constant_map.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/constant_map.dart b/sdk/lib/_internal/compiler/js_lib/constant_map.dart
index c3317b467a4fa1eef807ba3218339574fb24554c..ae3e3799f33ac8eb6c77435e38ec38ef9304aac5 100644
--- a/sdk/lib/_internal/compiler/js_lib/constant_map.dart
+++ b/sdk/lib/_internal/compiler/js_lib/constant_map.dart
@@ -114,7 +114,7 @@ class GeneralConstantMap<K, V> extends ConstantMap<K, V> {
   Map<K, V> _getMap() {
     LinkedHashMap<K, V> backingMap = JS('LinkedHashMap|Null', r'#.$map', this);
     if (backingMap == null) {
-      backingMap = new LinkedHashMap<K, V>();
+      backingMap = new JsLinkedHashMap<K, V>();
       fillLiteralMap(_jsData, backingMap);
       JS('', r'#.$map = #', this, backingMap);
     }