Finish strong mode cleaning of dart2js.

pkg/compiler/lib/src/universe/codegen_world_builder.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.
 
 part of world_builder;
 
 /// World builder specific to codegen.
 ///
 /// This adds additional access to liveness of selectors and elements.
 abstract class CodegenWorldBuilder implements WorldBuilder {
@@ skipping 544 matching lines @@
   void forEachInstanceField(
       ClassElement cls, void f(ClassEntity declarer, FieldEntity field)) {
     cls.implementation
         .forEachInstanceField(f, includeSuperAndInjectedMembers: true);
   }
 
   @override
   void forEachParameter(
       MethodElement function, void f(DartType type, String name)) {
     FunctionSignature parameters = function.functionSignature;
-    parameters.forEachParameter((ParameterElement parameter) {
+    parameters.forEachParameter((_parameter) {
+      ParameterElement parameter = _parameter;
       f(parameter.type, parameter.name);
     });
   }
 
   @override
   void _processInstantiatedClassMember(
       ClassEntity cls, MemberElement member, MemberUsedCallback memberUsed) {
     assert(member.isDeclaration, failedAt(member));
     if (member.isMalformed) return;
     super._processInstantiatedClassMember(cls, member, memberUsed);
@@ skipping 39 matching lines @@
 
   @override
   void forEachInstanceField(
       ClassEntity cls, void f(ClassEntity declarer, FieldEntity field)) {
     _elementEnvironment.forEachClassMember(cls,
         (ClassEntity declarer, MemberEntity member) {
       if (member.isField && member.isInstanceMember) f(declarer, member);
     });
   }
 }