Move parser and token related libraries into their own subfolder.

pkg/compiler/lib/src/dart_backend/backend_ast_to_frontend_ast.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 dart_tree_printer;
 
 import '../constants/values.dart' as values;
 import '../dart_types.dart' as types;
 import '../diagnostics/invariant.dart' show
     invariant;
 import '../elements/elements.dart' as elements;
 import '../resolution/tree_elements.dart' show
     TreeElementMapping;
+import '../tokens/token.dart';
 import '../tree/tree.dart' as tree;
-import '../scanner/token.dart';
 import '../util/util.dart';
 import 'backend_ast_nodes.dart';
 import 'backend_ast_emitter.dart' show TypeGenerator;
 
 /// Translates the backend AST to Dart frontend AST.
 tree.Node emit(TreeElementMapping treeElements,
                RootNode root) {
   return new TreePrinter(treeElements).makeDefinition(root);
 }
 
@@ skipping 1308 matching lines @@
             printStringChunk(chunk.previous),
             node);
       } else {
         return node;
       }
     }
     return printStringChunk(output.chunk);
   }
 
 }