Rework codegen tools to avoid relying on CWD; integrate with task model graph.

pkg/analyzer/tool/task_dependency_graph/check_test.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 task_dependency_graph.check_test;
 
 import 'dart:io';
 
 import 'package:path/path.dart';
 
 import 'generate.dart';
 
 /**
  * Check that the target file has been code generated.  If it hasn't tell the
  * user to run generate.dart.
  */
 main() {
   String script = Platform.script.toFilePath(windows: Platform.isWindows);
-  Driver driver = new Driver();
-  if (!driver.checkFile()) {
-    print('${driver.file.absolute} does not have expected contents.');
+  String pkgPath = normalize(join(dirname(script), '..', '..'));
+  if (!target.check(pkgPath)) {
+    print(
+        '${target.output(pkgPath).absolute} does not have expected contents.');
     print('Please regenerate using:');
     String executable = Platform.executable;
     String packageRoot = '';
     if (Platform.packageRoot.isNotEmpty) {
       packageRoot = ' --package-root=${Platform.packageRoot}';
     }
     String generateScript = join(dirname(script), 'generate.dart');
     print('  $executable$packageRoot $generateScript');
     exit(1);
   } else {
     print('Generated file is up to date.');
   }
 }