Use elements/types in constants/values

pkg/compiler/lib/src/js_backend/constant_system_javascript.dart

Index: pkg/compiler/lib/src/js_backend/constant_system_javascript.dart
diff --git a/pkg/compiler/lib/src/js_backend/constant_system_javascript.dart b/pkg/compiler/lib/src/js_backend/constant_system_javascript.dart
index 40dcd8ff1bd6d2c199bc4337df5502598a8e722e..1571c41cf36605d1de71aec544a3c1993ed1582e 100644
--- a/pkg/compiler/lib/src/js_backend/constant_system_javascript.dart
+++ b/pkg/compiler/lib/src/js_backend/constant_system_javascript.dart
@@ -320,10 +320,10 @@ class JavaScriptConstantSystem extends ConstantSystem {
 
   @override
   ConstantValue createType(Compiler compiler, ResolutionDartType type) {
-    return new TypeConstantValue(
-        type,
-        compiler.backend.backendClasses.typeImplementation
-            .computeType(compiler.resolution));
+    ResolutionInterfaceType instanceType = compiler
+        .backend.backendClasses.typeImplementation
+        .computeType(compiler.resolution);
+    return new TypeConstantValue(type, instanceType);
   }
 
   // Integer checks report true for -0.0, INFINITY, and -INFINITY.  At
@@ -382,7 +382,7 @@ class JavaScriptConstantSystem extends ConstantSystem {
     }
 
     bool hasProtoKey = (protoValue != null);
-    ResolutionDartType keysType;
+    ResolutionInterfaceType keysType;
     if (sourceType.treatAsRaw) {
       keysType = commonElements.listType();
     } else {