Add TypeVariable object on runtime to support reflection on type variables.

sdk/lib/_internal/compiler/implementation/js_emitter/js_emitter.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.js_emitter;
 
 import 'dart:collection' show LinkedHashMap, Queue;
 
 import '../common.dart';
 
@@ skipping 17 matching lines @@
     CheckedModeHelper,
     CheckedModeHelper,
     ConstantEmitter,
     JavaScriptBackend,
     JavaScriptBackend,
     Namer,
     NativeEmitter,
     RuntimeTypes,
     Substitution,
     TypeCheck,
-    TypeChecks;
+    TypeChecks,
+    TypeVariableConstantHandler;
 
 import '../source_file.dart' show
     SourceFile;
 
 import '../source_map_builder.dart' show
     SourceMapBuilder;
 
 import '../util/characters.dart' show
     $$,
     $A,
     $HASH,
     $PERIOD,
     $Z,
     $a,
     $z;
 
 import '../util/uri_extras.dart' show
     relativize;
 
 part 'class_builder.dart';
 part 'closure_invocation_element.dart';
 part 'code_emitter_task.dart';
 part 'container_builder.dart';
 part 'declarations.dart';
 part 'reflection_data_parser.dart';