Refactor code for checking that generated files are up to date.

pkg/analyzer/tool/task_dependency_graph/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 output a description of tasks and their
  * dependencies in ".dot" format.  Prior to running, the user should run "pub
  * get" in the analyzer directory to ensure that a "packages" folder exists.
  *
  * TODO(paulberry):
@@ skipping 23 matching lines @@
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:path/path.dart' as path;
 import 'package:path/path.dart';
 
 /**
  * Generate the target .dot file.
  */
 main() {
   String script = Platform.script.toFilePath(windows: Platform.isWindows);
   String pkgPath = normalize(join(dirname(script), '..', '..'));
-  target.generate(pkgPath);
+  GeneratedContent.generateAll(pkgPath, <GeneratedContent>[target]);
 }
 
 final GeneratedFile target = new GeneratedFile(
     'tool/task_dependency_graph/tasks.dot',
     (String pkgPath) => new Driver(pkgPath).generateFileContents());
 
 typedef void GetterFinderCallback(PropertyAccessorElement element);
 
 class Driver {
   PhysicalResourceProvider resourceProvider;
@@ skipping 254 matching lines @@
   @override
   visitIdentifier(Identifier node) {
     Element element = node.staticElement;
     if (element is PropertyAccessorElement &&
         element.isGetter &&
         element.returnType.isSubtypeOf(type)) {
       callback(element);
     }
   }
 }