Fix the locals lookup of variables and partial implementation of boxing of variables.

pkg/compiler/lib/src/universe/use.dart

Index: pkg/compiler/lib/src/universe/use.dart
diff --git a/pkg/compiler/lib/src/universe/use.dart b/pkg/compiler/lib/src/universe/use.dart
index 124f1815194b36a462133e030d03a1267355952b..1c5898d824015c6adfb76c51f7fef375c04f966a 100644
--- a/pkg/compiler/lib/src/universe/use.dart
+++ b/pkg/compiler/lib/src/universe/use.dart
@@ -20,6 +20,7 @@ import '../closure.dart' show BoxFieldElement;
 import '../common.dart';
 import '../constants/values.dart';
 import '../elements/types.dart';
+import '../js_model/closure.dart' show JRecord;
 import '../elements/elements.dart' show Element;
 import '../elements/entities.dart';
 import '../util/util.dart' show Hashing;
@@ -358,7 +359,9 @@ class StaticUse {
   /// Read access of an instance field or boxed field [element].
   factory StaticUse.fieldGet(FieldEntity element) {
     assert(
-        element.isInstanceMember || element is BoxFieldElement,
+        element.isInstanceMember ||
+            element is BoxFieldElement ||
+            element is JRecord,
         failedAt(element,
             "Field init element $element must be an instance or boxed field."));
     return new StaticUse.internal(element, StaticUseKind.FIELD_GET);
@@ -367,7 +370,9 @@ class StaticUse {
   /// Write access of an instance field or boxed field [element].
   factory StaticUse.fieldSet(FieldEntity element) {
     assert(
-        element.isInstanceMember || element is BoxFieldElement,
+        element.isInstanceMember ||
+            element is BoxFieldElement ||
+            element is JRecord,
         failedAt(element,
             "Field init element $element must be an instance or boxed field."));
     return new StaticUse.internal(element, StaticUseKind.FIELD_SET);