Add support for generating lints when using the new driver

pkg/analyzer/lib/src/services/lint.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 analyzer.src.services.lint;
 
 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.
 LintRegistry lintRegistry = new LintRegistry();
 
 /// Return lints associated with this [context], or an empty list if there are
 /// none.
 List<Linter> getLints(AnalysisContext context) =>
     context.analysisOptions.lintRules;
 
 /// Associate these [lints] with the given [context].
 void setLints(AnalysisContext context, List<Linter> lints) {
   AnalysisOptionsImpl options =
       new AnalysisOptionsImpl.from(context.analysisOptions);
   options.lintRules = lints;
   context.analysisOptions = options;
 }
 
 /// Implementers contribute lint warnings via the provided error [reporter].
 abstract class Linter {
   /// Used to report lint warnings.
   /// 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;
 
   /// Return a visitor to be passed to compilation units to perform lint
   /// analysis.
   /// Lint errors are reported via this [Linter]'s error [reporter].
   AstVisitor getVisitor();
 }
 
 /// Manages lint timing.
 class LintRegistry {
   /// Dictionary mapping lints (by name) to timers.
   final Map<String, Stopwatch> timers = new HashMap<String, Stopwatch>();
 
   /// Get a timer associated with the given lint rule (or create one if none
   /// exists).
   Stopwatch getTimer(Linter linter) =>
       timers.putIfAbsent(linter.name, () => new Stopwatch());
 }