Implement JsKernelToElementMap through KernelToElementMapBase

pkg/compiler/lib/src/kernel/env.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.kernel.env;
 
 import 'package:kernel/ast.dart' as ir;
 import 'package:kernel/clone.dart';
 import 'package:kernel/type_algebra.dart';
 
 import '../common.dart';
 import '../common/resolution.dart';
 import '../constants/constructors.dart';
 import '../constants/expressions.dart';
 import '../constants/values.dart';
 import '../elements/entities.dart';
 import '../elements/types.dart';
 import '../ordered_typeset.dart';
 import '../ssa/kernel_impact.dart';
 import 'element_map.dart';
 import 'element_map_impl.dart';
 import 'element_map_mixins.dart';
 
 /// Environment for fast lookup of program libraries.
 class ProgramEnv {
-  final Set<ir.Program> programs = new Set<ir.Program>();
+  final Set<ir.Program> _programs = new Set<ir.Program>();
 
   Map<Uri, LibraryEnv> _libraryMap;
 
   /// TODO(johnniwinther): Handle arbitrary load order if needed.
-  ir.Member get mainMethod => programs.first?.mainMethod;
+  ir.Member get mainMethod => _programs.first?.mainMethod;
 
   void addProgram(ir.Program program) {
-    if (programs.add(program)) {
+    if (_programs.add(program)) {
       if (_libraryMap != null) {
         _addLibraries(program);
       }
     }
   }
 
   void _addLibraries(ir.Program program) {
     for (ir.Library library in program.libraries) {
       _libraryMap[library.importUri] = new LibraryEnv(library);
     }
   }
 
   void _ensureLibraryMap() {
     if (_libraryMap == null) {
       _libraryMap = <Uri, LibraryEnv>{};
-      for (ir.Program program in programs) {
+      for (ir.Program program in _programs) {
         _addLibraries(program);
       }
     }
   }
 
   /// Return the [LibraryEnv] for the library with the canonical [uri].
   LibraryEnv lookupLibrary(Uri uri) {
     _ensureLibraryMap();
     return _libraryMap[uri];
   }
@@ skipping 339 matching lines @@
       } else {
         throw new SpannableAssertionFailure(
             field,
             "Unexpected field $field in "
             "KernelWorldBuilder._getConstructorConstant");
       }
     }
     return _constant;
   }
 }