Starting making dart2js strong mode clean.

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

 // Copyright (c) 2014, 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.maplet;
 
 import 'dart:collection' show MapBase, IterableBase;
 
 class Maplet<K, V> extends MapBase<K, V> {
-  static const _MARKER = const _MapletMarker();
-  static const CAPACITY = 8;
+  static const _MapletMarker _MARKER = const _MapletMarker();
+  static const int CAPACITY = 8;
 
 // The maplet can be in one of four states:
   //
   //   * Empty          (extra: null,   key: marker, value: null)
   //   * Single element (extra: null,   key: key,    value: value)
   //   * List-backed    (extra: length, key: list,   value: null)
   //   * Map-backed     (extra: marker, key: map,    value: null)
   //
   // When the maplet is list-backed, the list has two sections: One
   // for keys and one for values. The first [CAPACITY] entries are
   // the keys and they may contain markers for deleted elements. After
   // the keys there are [CAPACITY] entries for the values.
 
-  var _key = _MARKER;
+  dynamic _key = _MARKER;
   var _value;
   var _extra;
 
   Maplet();
 
   Maplet.from(Maplet<K, V> other) {
     other.forEach((K key, V value) {
       this[key] = value;
     });
   }
@@ skipping 235 matching lines @@
       if (Maplet._MARKER != candidate) {
         _current = candidate;
         _remaining--;
         return true;
       }
     }
     _current = null;
     return false;
   }
 }