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

pkg/analyzer/tool/task_dependency_graph/check_test.dart

Index: pkg/analyzer/tool/task_dependency_graph/check_test.dart
diff --git a/pkg/analyzer/tool/task_dependency_graph/check_test.dart b/pkg/analyzer/tool/task_dependency_graph/check_test.dart
index b64bf521c5c6948a80902e76f75d57d959bcec38..3d64a855eedf8c2a07be81f505ec5e7075a58157 100644
--- a/pkg/analyzer/tool/task_dependency_graph/check_test.dart
+++ b/pkg/analyzer/tool/task_dependency_graph/check_test.dart
@@ -6,6 +6,7 @@ library task_dependency_graph.check_test;
 
 import 'dart:io';
 
+import 'package:analyzer/src/codegen/tools.dart';
 import 'package:path/path.dart';
 
 import 'generate.dart';
@@ -17,19 +18,6 @@ import 'generate.dart';
 main() {
   String script = Platform.script.toFilePath(windows: Platform.isWindows);
   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.');
-  }
+  GeneratedContent.checkAll(pkgPath, 'tool/task_dependency_graph/generate.dart',
+      <GeneratedContent>[target]);
 }