Move ElementEnvironment.isSubtype to DartTypes

pkg/compiler/lib/src/frontend_strategy.dart

 // Copyright (c) 2017, 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.
 
 library dart2js.frontend_strategy;
 
 import 'common.dart';
 import 'common_elements.dart';
 import 'common/backend_api.dart';
 import 'common/tasks.dart';
 import 'elements/entities.dart';
+import 'elements/types.dart';
 import 'environment.dart';
 import 'enqueue.dart';
 import 'js_backend/backend.dart';
 import 'js_backend/backend_usage.dart';
 import 'js_backend/custom_elements_analysis.dart';
 import 'js_backend/interceptor_data.dart';
 import 'js_backend/mirrors_analysis.dart';
 import 'js_backend/mirrors_data.dart';
 import 'js_backend/native_data.dart';
 import 'js_backend/no_such_method_registry.dart';
@@ skipping 17 matching lines @@
       PatchResolverFunction patchResolverFunc,
       PatchParserTask patchParser,
       Environment environment,
       DiagnosticReporter reporter,
       Measurer measurer);
 
   /// Returns the [ElementEnvironment] for the element model used in this
   /// strategy.
   ElementEnvironment get elementEnvironment;
 
+  /// Returns the [DartTypes] for the element model used in this strategy.
+  DartTypes get dartTypes;
+
   /// Returns the [AnnotationProcessor] for this strategy.
   AnnotationProcessor get annotationProcesser;
 
   /// Creates the [NativeClassFinder] for this strategy.
   NativeClassFinder createNativeClassFinder(NativeBasicData nativeBasicData);
 
   /// Creates the [NoSuchMethodResolver] corresponding the resolved model of
   /// this strategy.
   NoSuchMethodResolver createNoSuchMethodResolver();
 
@@ skipping 37 matching lines @@
 abstract class AnnotationProcessor {
   void extractNativeAnnotations(
       LibraryEntity library, NativeBasicDataBuilder nativeBasicDataBuilder);
 
   void extractJsInteropAnnotations(
       LibraryEntity library, NativeBasicDataBuilder nativeBasicDataBuilder);
 
   void processJsInteropAnnotations(
       NativeBasicData nativeBasicData, NativeDataBuilder nativeDataBuilder);
 }