Begin refactoring compiler out of diet parser and scanner

pkg/compiler/lib/src/parser/diet_parser_task.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.
 
 library dart2js.parser.diet.task;
 
 import '../common.dart';
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart' show Compiler;
 import '../elements/elements.dart' show CompilationUnitElement;
+import '../id_generator.dart';
 import '../tokens/token.dart' show Token;
 
 import 'listener.dart' show ParserError;
 import 'element_listener.dart' show ElementListener, ScannerOptions;
 import '../options.dart' show ParserOptions;
 import 'partial_parser.dart' show PartialParser;
 
 class DietParserTask extends CompilerTask {
   final ParserOptions _parserOptions;
+  final IdGenerator _idGenerator;
 
-  DietParserTask(Compiler compiler, this._parserOptions) : super(compiler);
+  DietParserTask(Compiler compiler, this._parserOptions, this._idGenerator)
+      : super(compiler);
 
   final String name = 'Diet Parser';
 
   dietParse(CompilationUnitElement compilationUnit, Token tokens) {
     measure(() {
-      Function idGenerator = compiler.getNextFreeClassId;
       ScannerOptions scannerOptions =
           new ScannerOptions.from(compiler, compilationUnit.library);
       ElementListener listener = new ElementListener(
-          scannerOptions, compiler.reporter, compilationUnit, idGenerator);
+          scannerOptions, compiler.reporter, compilationUnit, _idGenerator);
       PartialParser parser = new PartialParser(listener, _parserOptions);
       try {
         parser.parseUnit(tokens);
       } on ParserError catch (_) {
         assert(invariant(compilationUnit, compiler.compilationFailed));
       }
     });
   }
 }