Move incremental scanner to separate file

pkg/analyzer/lib/src/generated/engine.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.
 
 // This code was auto-generated, is not intended to be edited, and is subject to
 // significant change. Please see the README file for more information.
 
 library engine;
 
 import "dart:math" as math;
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/task/task_dart.dart';
 
 import 'ast.dart';
 import 'constant.dart';
 import 'element.dart';
 import 'error.dart';
 import 'error_verifier.dart';
 import 'html.dart' as ht;
+import 'incremental_scanner.dart';
 import 'incremental_resolver.dart' show IncrementalResolver;
 import 'instrumentation.dart';
 import 'java_core.dart';
 import 'java_engine.dart';
 import 'parser.dart' show Parser, IncrementalParser;
 import 'resolver.dart';
 import 'scanner.dart';
 import 'sdk.dart' show DartSdk;
 import 'source.dart';
 import 'utilities_collection.dart';
@@ skipping 14774 matching lines @@
 
   @override
   Object visitPolymerTagDartElement(PolymerTagDartElement element) {
     if (element.name == PolymerHtmlUnitBuilder_this._elementName) {
       throw new PolymerHtmlUnitBuilder_FoundTagDartElementError(
           element as PolymerTagDartElementImpl);
     }
     return null;
   }
 }