Break up another large file

pkg/analyzer/tool/summary/generate.dart

 // Copyright (c) 2015, 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 file contains code to generate serialization/deserialization logic for
  * summaries based on an "IDL" description of the summary format (written in
  * stylized Dart).
  *
  * For each class in the "IDL" input, two corresponding classes are generated:
  * - A class with the same name which represents deserialized summary data in
  *   memory.  This class has read-only semantics.
  * - A "builder" class which can be used to generate serialized summary data.
  *   This class has write-only semantics.
  *
  * Each of the "builder" classes has a single `finish` method which writes
  * the entity being built into the given FlatBuffer and returns the `Offset`
  * reference to it.
  */
 library analyzer.tool.summary.generate;
 
 import 'dart:convert';
 import 'dart:io' hide File;
 
 import 'package:analyzer/analyzer.dart';
 import 'package:analyzer/dart/ast/token.dart';
+import 'package:analyzer/error/listener.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/physical_file_system.dart';
 import 'package:analyzer/src/codegen/tools.dart';
 import 'package:analyzer/src/dart/scanner/reader.dart';
 import 'package:analyzer/src/dart/scanner/scanner.dart';
 import 'package:analyzer/src/generated/parser.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:path/path.dart';
 
 import 'idl_model.dart' as idlModel;
@@ skipping 986 matching lines @@
       return token.lexeme.split('\n').map((String line) {
         if (line.startsWith(indent)) {
           line = line.substring(indent.length);
         }
         return line;
       }).join('\n');
     }
     return null;
   }
 }