Remove BackendClasses and JavaScriptBackendClasses.

pkg/compiler/lib/src/compile_time_constants.dart

Index: pkg/compiler/lib/src/compile_time_constants.dart
diff --git a/pkg/compiler/lib/src/compile_time_constants.dart b/pkg/compiler/lib/src/compile_time_constants.dart
index 3c4fc5e93732a1bb132861ee6a84ad6584a819fb..883a124aa5f426f6691c68ee6aee3c6544a80564 100644
--- a/pkg/compiler/lib/src/compile_time_constants.dart
+++ b/pkg/compiler/lib/src/compile_time_constants.dart
@@ -4,7 +4,6 @@
 
 library dart2js.compile_time_constant_evaluator;
 
-import 'common/backend_api.dart' show BackendClasses;
 import 'common/resolution.dart' show Resolution;
 import 'common/tasks.dart' show CompilerTask, Measurer;
 import 'common.dart';
@@ -507,11 +506,7 @@ class CompileTimeConstantEvaluator extends Visitor<AstConstant> {
         node,
         new MapConstantExpression(type, keyExpressions, valueExpressions),
         constantSystem.createMap(
-            compiler.commonElements,
-            compiler.backend.backendClasses,
-            type,
-            keyValues,
-            map.values.toList()));
+            compiler.commonElements, type, keyValues, map.values.toList()));
   }
 
   AstConstant visitLiteralNull(LiteralNull node) {
@@ -606,8 +601,7 @@ class CompileTimeConstantEvaluator extends Visitor<AstConstant> {
   }
 
   ConstantValue makeTypeConstant(ResolutionDartType elementType) {
-    return constantSystem.createType(
-        compiler.commonElements, compiler.backend.backendClasses, elementType);
+    return constantSystem.createType(compiler.commonElements, elementType);
   }
 
   /// Returns true if the prefix of the send resolves to a deferred import
@@ -1453,9 +1447,6 @@ class _CompilerEnvironment implements Environment {
   _CompilerEnvironment(this._compiler);
 
   @override
-  BackendClasses get backendClasses => _compiler.backend.backendClasses;
-
-  @override
   CommonElements get commonElements => _compiler.commonElements;
 
   @override