Fix typing in dart2js serialization.

pkg/compiler/lib/src/serialization/serialization.dart

 // Copyright (c) 2015, 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.serialization;
 
 import 'package:front_end/src/scanner/token.dart' show TokenType;
 
 import '../common.dart';
 import '../common/resolution.dart';
@@ skipping 244 matching lines @@
     List<Value> list = <Value>[];
     _map[key] = new ListValue(list);
     return new ListEncoder(_serializer, list);
   }
 
   String toString() => _map.toString();
 }
 
 /// [ObjectDecoder] reads serialized values from a [Map] encoded from an
 /// [ObjectValue] where properties are stored using [Key] values as keys.
-class ObjectDecoder extends AbstractDecoder<Key> {
+class ObjectDecoder extends AbstractDecoder<dynamic, Key> {
   /// Creates an [ObjectDecoder] that decodes [map] into deserialized values
   /// using [deserializer] to create canonicalized values.
   ObjectDecoder(Deserializer deserializer, Map map) : super(deserializer, map);
 
   @override
   _getKeyValue(Key key) => _deserializer.decoder.getObjectPropertyValue(key);
 }
 
 /// [MapDecoder] reads serialized values from a [Map] encoded from an
 /// [MapValue] where entries are stored using [String] values as keys.
-class MapDecoder extends AbstractDecoder<String> {
+class MapDecoder extends AbstractDecoder<String, String> {
   /// Creates an [MapDecoder] that decodes [map] into deserialized values
   /// using [deserializer] to create canonicalized values.
   MapDecoder(Deserializer deserializer, Map<String, dynamic> map)
       : super(deserializer, map);
 
   @override
-  _getKeyValue(String key) => key;
+  String _getKeyValue(String key) => key;
 
   /// Applies [f] to every key in the decoded [Map].
   void forEachKey(f(String key)) {
     _map.keys.forEach(f);
   }
 }
 
 /// [ListDecoder] reads serialized map or object values from a [List].
 class ListDecoder {
   final Deserializer _deserializer;
@@ skipping 12 matching lines @@
     return new ObjectDecoder(_deserializer, _list[index]);
   }
 
   /// Returns an [MapDecoder] for the [index]th map value in the decoded list.
   MapDecoder getMap(int index) {
     return new MapDecoder(_deserializer, _list[index]);
   }
 }
 
 /// Abstract base implementation for [ObjectDecoder] and [MapDecoder].
-abstract class AbstractDecoder<K> {
+abstract class AbstractDecoder<M, K> {
   final Deserializer _deserializer;
-  final Map<K, dynamic> _map;
+  final Map<M, dynamic> _map;
 
   AbstractDecoder(this._deserializer, this._map) {
     assert(_deserializer != null);
     assert(_map != null);
   }
 
   /// Returns the value for [key] defined by the [SerializationDecoder] in used
   /// [_deserializer].
-  _getKeyValue(K key);
+  M _getKeyValue(K key);
 
   /// Returns `true` if [key] has an associated value in the decoded object.
   bool containsKey(K key) => _map.containsKey(_getKeyValue(key));
 
   /// Returns the enum value from the [enumValues] associated with [key] in the
   /// decoded object.
   ///
   /// If no value is associated with [key], then if [isOptional] is `true`,
   /// [defaultValue] is returned, otherwise an exception is thrown.
   getEnum(K key, List enumValues, {bool isOptional: false, defaultValue}) {
@@ skipping 813 matching lines @@
 
   /// Returns the value used to store [key] as a property in the encoding an
   /// [ObjectValue].
   ///
   /// Different encodings have different restrictions and capabilities as how
   /// to store a [Key] value. For instance: A JSON encoding needs to convert
   /// [Key] to a [String] to store it in a JSON object; a Dart encoding can
   /// choose to store a [Key] as an [int] or as the [Key] itself.
   getObjectPropertyValue(Key key);
 }