Add support for generating lints when using the new driver

pkg/analyzer/lib/src/services/lint.dart

Index: pkg/analyzer/lib/src/services/lint.dart
diff --git a/pkg/analyzer/lib/src/services/lint.dart b/pkg/analyzer/lib/src/services/lint.dart
index 097a8df3bfe1412c8511fdf01ffcdff76c39cc9b..af6a3ee1a001d97dfde904322dc8fb35cb081766 100644
--- a/pkg/analyzer/lib/src/services/lint.dart
+++ b/pkg/analyzer/lib/src/services/lint.dart
@@ -8,6 +8,7 @@ import 'dart:collection';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/error/listener.dart';
+import 'package:analyzer/src/dart/error/lint_codes.dart';
 import 'package:analyzer/src/generated/engine.dart';
 
 /// Shared lint registry.
@@ -32,6 +33,11 @@ abstract class Linter {
   /// NOTE: this is set by the framework before visit begins.
   ErrorReporter reporter;
 
+  /**
+   * Return the lint code associated with this linter.
+   */
+  LintCode get lintCode => null;
+
   /// Linter name.
   String get name;