Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/typechecker.dart

Index: pkg/compiler/lib/src/typechecker.dart
diff --git a/pkg/compiler/lib/src/typechecker.dart b/pkg/compiler/lib/src/typechecker.dart
index 2d854a2e59e3aabcfca6a687929362a93ad6a576..86d85d02a0a5be85b7c998d3d98dc8c786114ac8 100644
--- a/pkg/compiler/lib/src/typechecker.dart
+++ b/pkg/compiler/lib/src/typechecker.dart
@@ -2,7 +2,55 @@
 // 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.
 
-part of dart2js;
+library dart2js.typechecker;
+
+import 'constants/expressions.dart';
+import 'constants/values.dart';
+import 'core_types.dart';
+import 'dart2jslib.dart' show
+    Compiler,
+    CompilerTask,
+    invariant,
+    isPrivateName;
+import 'dart_types.dart';
+import 'elements/elements.dart' show
+    AbstractFieldElement,
+    AstElement,
+    AsyncMarker,
+    ClassElement,
+    ConstructorElement,
+    Element,
+    Elements,
+    EnumClassElement,
+    ExecutableElement,
+    FieldElement,
+    FunctionElement,
+    GetterElement,
+    InitializingFormalElement,
+    LibraryElement,
+    Member,
+    MemberSignature,
+    Name,
+    ParameterElement,
+    PrivateName,
+    PublicName,
+    ResolvedAst,
+    SetterElement,
+    TypeDeclarationElement,
+    TypedElement,
+    TypedefElement,
+    VariableElement;
+import 'messages.dart';
+import 'resolution/resolution.dart' show
+    TreeElements;
+import 'resolution/class_members.dart' show
+    MembersCreator;
+import 'tree/tree.dart';
+import 'util/util.dart' show
+    Link,
+    LinkBuilder,
+    Spannable;
+import '../compiler_new.dart' as api;
 
 class TypeCheckerTask extends CompilerTask {
   TypeCheckerTask(Compiler compiler) : super(compiler);