Starting making dart2js strong mode clean.

pkg/compiler/lib/src/util/setlet.dart

 // Copyright (c) 2013, 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.util.setlet;
 
 import 'dart:collection' show IterableBase;
 
 class Setlet<E> extends IterableBase<E> implements Set<E> {
-  static const _MARKER = const _SetletMarker();
-  static const CAPACITY = 8;
+  static const _SetletMarker _MARKER = const _SetletMarker();
+  static const int CAPACITY = 8;
 
   // The setlet can be in one of four states:
   //
   //   * Empty          (extra: null,   contents: marker)
   //   * Single element (extra: null,   contents: element)
   //   * List-backed    (extra: length, contents: list)
   //   * Set-backed     (extra: marker, contents: set)
   //
   // When the setlet is list-backed, the list in the contents field
   // may have empty slots filled with the marker value.
-  var _contents = _MARKER;
+  dynamic _contents = _MARKER;
   var _extra;
 
   Setlet();
   Setlet.from(Iterable<E> elements) {
     addAll(elements);
   }
 
   Iterator<E> get iterator {
     if (_extra == null) {
       return new _SetletSingleIterator<E>(_contents);
@@ skipping 273 matching lines @@
       if (Setlet._MARKER != candidate) {
         _current = candidate;
         _remaining--;
         return true;
       }
     }
     _current = null;
     return false;
   }
 }