dart2js: Fix hints in code base.

pkg/compiler/lib/src/dart_backend/backend.dart

 // Copyright (c) 2012, 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.
 
 part of dart_backend;
 
 // TODO(ahe): This class is simply wrong.  This backend should use
 // elements when it can, not AST nodes.  Perhaps a [Map<Element,
 // TreeElements>] is what is needed.
 class ElementAst {
@@ skipping 132 matching lines @@
    */
   @override
   bool shouldOutput(Element element) {
     return (!element.library.isPlatformLibrary &&
             !element.isSynthesized &&
             element is! AbstractFieldElement)
         || mirrorRenamer.isMirrorHelperLibrary(element.library);
   }
 
   int assembleProgram() {
-    ElementAstCreationContext context =
-        new _ElementAstCreationContext(compiler, constantSystem);
-
     ElementAst computeElementAst(AstElement element) {
       return new ElementAst(element.resolvedAst.node,
                             element.resolvedAst.elements);
     }
 
     // TODO(johnniwinther): Remove the need for this method.
     void postProcessElementAst(
         AstElement element, ElementAst elementAst,
         newTypedefElementCallback,
         newClassElementCallback) {
@@ skipping 340 matching lines @@
   }
 
   // TODO(johnniwinther): Remove this when values are computed from the
   // expressions.
   @override
   void copyConstantValues(DartConstantTask task) {
     constantCompiler.constantValueMap.addAll(
         task.constantCompiler.constantValueMap);
   }
 }
-
-abstract class ElementAstCreationContext {
-  DartTypes get dartTypes;
-  ConstantSystem get constantSystem;
-  InternalErrorFunction get internalError;
-}
-
-class _ElementAstCreationContext implements ElementAstCreationContext {
-  final Compiler compiler;
-  final ConstantSystem constantSystem;
-
-  _ElementAstCreationContext(this.compiler, this.constantSystem);
-
-  DartTypes get dartTypes => compiler.types;
-
-  InternalErrorFunction get internalError => compiler.internalError;
-}