dartj2s: add constructor helpers for map literals with no type parameters.

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

Index: sdk/lib/_internal/compiler/js_lib/collection_patch.dart
diff --git a/sdk/lib/_internal/compiler/js_lib/collection_patch.dart b/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
index 9242d392644fff7ec59795c0debf71fa905b9f4b..42b7fc9ec77d975c3d207021ae6b0fc03f7fd8bf 100644
--- a/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
+++ b/sdk/lib/_internal/compiler/js_lib/collection_patch.dart
@@ -529,6 +529,17 @@ class LinkedHashMap<K, V> {
   factory LinkedHashMap._empty() {
     return new JsLinkedHashMap<K, V>();
   }
+
+  // Private factory static function called by generated code for map literals.
+  // This version is for map literals without type parameters.
+  @NoInline()
+  static _makeEmpty() => new JsLinkedHashMap();
+
+  // Private factory static function called by generated code for map literals.
+  // This version is for map literals without type parameters.
+  @NoInline()
+  static _makeLiteral(keyValuePairs) =>
+      fillLiteralMap(keyValuePairs, new JsLinkedHashMap());
 }
 
 class _LinkedIdentityHashMap<K, V> extends JsLinkedHashMap<K, V> {