Fix dart2js warnings and add test to ensure it stays clean.

pkg/compiler/lib/src/resolution/resolution.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.
 
 library dart2js.resolution;
 
 import 'dart:collection' show Queue;
 
 import '../common.dart';
 import '../common/names.dart' show Identifiers;
@@ skipping 785 matching lines @@
     reporter.reportError(error, infos);
   }
 
   void checkClassMembers(ClassElement cls) {
     assert(invariant(cls, cls.isDeclaration));
     if (cls.isObject) return;
     // TODO(johnniwinther): Should this be done on the implementation element as
     // well?
     List<Element> constConstructors = <Element>[];
     List<Element> nonFinalInstanceFields = <Element>[];
-    cls.forEachMember((holder, member) {
+    cls.forEachMember((holder, dynamic member) {
       reporter.withCurrentElement(member, () {
         // Perform various checks as side effect of "computing" the type.
         member.computeType(resolution);
 
         // Check modifiers.
+        // ignore: UNDEFINED_GETTER
         if (member.isFunction && member.modifiers.isFinal) {
           reporter.reportErrorMessage(
               member, MessageKind.ILLEGAL_FINAL_METHOD_MODIFIER);
         }
         if (member.isConstructor) {
+          // ignore: UNDEFINED_GETTER
           final mismatchedFlagsBits = member.modifiers.flags &
               (Modifiers.FLAG_STATIC | Modifiers.FLAG_ABSTRACT);
           if (mismatchedFlagsBits != 0) {
             final mismatchedFlags =
                 new Modifiers.withFlags(null, mismatchedFlagsBits);
             reporter.reportErrorMessage(
                 member,
                 MessageKind.ILLEGAL_CONSTRUCTOR_MODIFIERS,
                 {'modifiers': mismatchedFlags});
           }
+          // ignore: UNDEFINED_GETTER
           if (member.modifiers.isConst) {
             constConstructors.add(member);
           }
         }
         if (member.isField) {
+          // ignore: UNDEFINED_GETTER
           if (member.modifiers.isConst && !member.modifiers.isStatic) {
             reporter.reportErrorMessage(
                 member, MessageKind.ILLEGAL_CONST_FIELD_MODIFIER);
           }
+          // ignore: UNDEFINED_GETTER
           if (!member.modifiers.isStatic && !member.modifiers.isFinal) {
             nonFinalInstanceFields.add(member);
           }
         }
         checkAbstractField(member);
         checkUserDefinableOperator(member);
       });
     });
     if (!constConstructors.isEmpty && !nonFinalInstanceFields.isEmpty) {
       Spannable span =
@@ skipping 293 matching lines @@
   TreeElements get treeElements {
     assert(invariant(this, _treeElements != null,
         message: "TreeElements have not been computed for $this."));
     return _treeElements;
   }
 
   void reuseElement() {
     _treeElements = null;
   }
 }