Move dart2jslib parts into separate libraries.

pkg/compiler/lib/src/mirrors_used.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.mirrors_used;
 
 import 'compile_time_constants.dart' show
     ConstantCompiler;
 import 'constants/expressions.dart';
 import 'constants/values.dart' show
     ConstantValue,
     ConstructedConstantValue,
     ListConstantValue,
     StringConstantValue,
     TypeConstantValue;
-
 import 'dart_types.dart' show
     DartType,
     InterfaceType,
     TypeKind;
-
 import 'dart2jslib.dart' show
     Compiler,
     CompilerTask,
-    MessageKind,
-    TreeElements,
     invariant;
-
 import 'elements/elements.dart' show
     ClassElement,
     Element,
     LibraryElement,
     MetadataAnnotation,
     ScopeContainerElement,
     VariableElement;
-
+import 'messages.dart' show
+    MessageKind;
+import 'resolution/resolution.dart' show
+    TreeElements;
 import 'tree/tree.dart' show
     Import,
     LibraryTag,
     NamedArgument,
     NewExpression,
     Node;
-
 import 'util/util.dart' show
     Link,
     Spannable;
 
 /**
  * Compiler task that analyzes MirrorsUsed annotations.
  *
  * When importing 'dart:mirrors', it is possible to annotate the import with
  * MirrorsUsed annotation.  This is a way to declare what elements will be
  * reflected on at runtime.  Such elements, even they would normally be
@@ skipping 536 matching lines @@
       // @MirrorsUsed(targets: fisk)
       //                       ^^^^
       //
       // Instead of saying 'fisk' should pretty print the problematic constant
       // value.
       return spannable;
     }
     return node;
   }
 }