Remove BackendClasses and JavaScriptBackendClasses.

pkg/compiler/lib/src/constants/evaluation.dart

Index: pkg/compiler/lib/src/constants/evaluation.dart
diff --git a/pkg/compiler/lib/src/constants/evaluation.dart b/pkg/compiler/lib/src/constants/evaluation.dart
index bf0d833afbb10aee09b3ce2457f00ee54e7154a5..2fb8c7b626b28dfc80108540a7ad53101ef1dd42 100644
--- a/pkg/compiler/lib/src/constants/evaluation.dart
+++ b/pkg/compiler/lib/src/constants/evaluation.dart
@@ -5,7 +5,6 @@
 library dart2js.constants.evaluation;
 
 import '../common.dart';
-import '../common/backend_api.dart' show BackendClasses;
 import '../common_elements.dart' show CommonElements;
 import '../elements/entities.dart';
 import '../elements/types.dart';
@@ -15,12 +14,8 @@ import 'expressions.dart';
 
 /// Environment used for evaluating constant expressions.
 abstract class Environment {
-  // TODO(johnniwinther): Replace this with [CommonElements] and maybe
-  // [Backend].
   CommonElements get commonElements;
 
-  BackendClasses get backendClasses;
-
   /// Read environments string passed in using the '-Dname=value' option.
   String readFromEnvironment(String name);