Use entities in the TypeMask interface.

tests/compiler/dart2js/simple_inferrer_test.dart

Index: tests/compiler/dart2js/simple_inferrer_test.dart
diff --git a/tests/compiler/dart2js/simple_inferrer_test.dart b/tests/compiler/dart2js/simple_inferrer_test.dart
index fb5467451209ebe7f0b96eeb3285968d9b6df0ec..f3dbf3e174a9c98a796c2db9490c783d443895da 100644
--- a/tests/compiler/dart2js/simple_inferrer_test.dart
+++ b/tests/compiler/dart2js/simple_inferrer_test.dart
@@ -872,10 +872,9 @@ void main() {
         checkFactoryConstructor('A', '');
 
         checkReturn('testCascade1', commonMasks.growableListType);
-        checkReturn(
-            'testCascade2',
-            new TypeMask.nonNullExact(
-                findElement(compiler, 'CascadeHelper'), closedWorld));
+        ClassElement clsCascadeHelper = findElement(compiler, 'CascadeHelper');
+        checkReturn('testCascade2',
+            new TypeMask.nonNullExact(clsCascadeHelper, closedWorld));
         checkReturn('testSpecialization1', commonMasks.numType);
         checkReturn('testSpecialization2', commonMasks.dynamicType);
         checkReturn('testSpecialization3', commonMasks.uint31Type.nullable());