Add stub versions of KernelInferrerEngine and friends

tests/compiler/dart2js/map_tracer_test.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'package:compiler/src/types/types.dart' show MapTypeMask, TypeMask;
 
 import 'compiler_helper.dart';
 import 'type_mask_test_helper.dart';
@@ skipping 189 matching lines @@
 
 void main() {
   // Test empty literal map
   doTest('{}');
   // Test preset map of <String,uint32>
   doTest('{presetKey : anInt}', "presetKey", "anInt");
   // Test preset map of <Double,uint32>
   doTest('{aDouble : anInt}', "aDouble", "anInt");
 }
 
-void doTest(String allocation, [String keyElement, String valueElement]) {
+void doTest(String allocation,
+    [String keyElementName, String valueElementName]) {
   Uri uri = new Uri(scheme: 'source');
   var compiler = compilerFor(generateTest(allocation), uri,
       expectedErrors: 0, expectedWarnings: 1);
   asyncTest(() => compiler.run(uri).then((_) {
         var keyType, valueType;
         var typesInferrer = compiler.globalInference.typesInferrerInternal;
         var closedWorld = typesInferrer.closedWorld;
         var commonMasks = closedWorld.commonMasks;
         var emptyType = new TypeMask.nonNullEmpty();
-        var aKeyType =
-            typesInferrer.getTypeOfMember(findElement(compiler, 'aKey'));
-        if (keyElement != null) {
-          keyType =
-              typesInferrer.getTypeOfMember(findElement(compiler, keyElement));
+        MemberElement aKey = findElement(compiler, 'aKey');
+        var aKeyType = typesInferrer.getTypeOfMember(aKey);
+        if (keyElementName != null) {
+          MemberElement keyElement = findElement(compiler, keyElementName);
+          keyType = typesInferrer.getTypeOfMember(keyElement);
         }
-        if (valueElement != null) {
-          valueType = typesInferrer
-              .getTypeOfMember(findElement(compiler, valueElement));
+        if (valueElementName != null) {
+          MemberElement valueElement = findElement(compiler, valueElementName);
+          valueType = typesInferrer.getTypeOfMember(valueElement);
         }
         if (keyType == null) keyType = emptyType;
         if (valueType == null) valueType = emptyType;
 
         checkType(String name, keyType, valueType) {
-          var element = findElement(compiler, name);
+          MemberElement element = findElement(compiler, name);
           MapTypeMask mask = typesInferrer.getTypeOfMember(element);
           Expect.equals(keyType, simplify(mask.keyType, closedWorld), name);
           Expect.equals(valueType, simplify(mask.valueType, closedWorld), name);
         }
 
         K(TypeMask other) =>
             simplify(keyType.union(other, closedWorld), closedWorld);
         V(TypeMask other) =>
             simplify(valueType.union(other, closedWorld), closedWorld)
                 .nullable();
@@ skipping 33 matching lines @@
         checkType('mapStoredInListButEscapes', K(commonMasks.dynamicType),
             V(commonMasks.dynamicType));
         checkType('mapStoredInMap', K(aKeyType), V(commonMasks.uint31Type));
         checkType('mapStoredInMapButEscapes', K(commonMasks.dynamicType),
             V(commonMasks.dynamicType));
 
         checkType('mapUnset', K(emptyType), V(emptyType));
         checkType('mapOnlySetWithConstraint', K(aKeyType), V(emptyType));
       }));
 }