Move TypeMask.simplify to a test helper.

tests/compiler/dart2js/map_tracer_test.dart

Index: tests/compiler/dart2js/map_tracer_test.dart
diff --git a/tests/compiler/dart2js/map_tracer_test.dart b/tests/compiler/dart2js/map_tracer_test.dart
index 8dc4fcd606093ac4aefd14e3cb9e48d9249f0080..79eeebc1abef86abfa5054110e932e50b012d05c 100644
--- a/tests/compiler/dart2js/map_tracer_test.dart
+++ b/tests/compiler/dart2js/map_tracer_test.dart
@@ -10,6 +10,7 @@ import
 
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
+import 'type_mask_test_helper.dart';
 
 
 String generateTest(String mapAllocation) {
@@ -236,12 +237,12 @@ void doTest(String allocation, [String keyElement,
     checkType(String name, keyType, valueType) {
       var element = findElement(compiler, name);
       MapTypeMask mask = typesInferrer.getTypeOfElement(element);
-      Expect.equals(keyType, mask.keyType.simplify(compiler), name);
-      Expect.equals(valueType, mask.valueType.simplify(compiler), name);
+      Expect.equals(keyType, simplify(mask.keyType, compiler), name);
+      Expect.equals(valueType, simplify(mask.valueType, compiler), name);
     }
 
-    K(TypeMask other) => keyType.union(other, compiler).simplify(compiler);
-    V(TypeMask other) => valueType.union(other, compiler).simplify(compiler);
+    K(TypeMask other) => simplify(keyType.union(other, compiler), compiler);
+    V(TypeMask other) => simplify(valueType.union(other, compiler), compiler);
 
     checkType('mapInField', K(aKeyType), V(typesTask.numType));
     checkType('mapPassedToMethod', K(aKeyType), V(typesTask.numType));