Rearranges the polymer package now that the old compiler is gone.

pkg/polymer/lib/src/build/code_extractor.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.
 
 /** Transfomer that extracts inlined script code into separate assets. */
-library polymer.src.transformers;
+library polymer.src.build.code_extractor;
 
 import 'dart:async';
 
 import 'package:analyzer_experimental/src/generated/ast.dart';
 import 'package:analyzer_experimental/src/generated/error.dart';
 import 'package:analyzer_experimental/src/generated/parser.dart';
 import 'package:analyzer_experimental/src/generated/scanner.dart';
 import 'package:barback/barback.dart';
 import 'package:path/path.dart' as path;
 
@@ skipping 57 matching lines @@
   var errorListener = new _ErrorCollector();
   var token = new StringScanner(null, code, errorListener).tokenize();
   var unit = new Parser(null, errorListener).parseCompilationUnit(token);
   return unit.directives.any((d) => d is LibraryDirective);
 }
 
 class _ErrorCollector extends AnalysisErrorListener {
   final errors = <AnalysisError>[];
   onError(error) => errors.add(error);
 }