Add more options to configure the linter.

pkg/polymer/lib/src/build/linter.dart

 // Copyright (c) 2013, 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.
 
 /// Logic to validate that developers are correctly using Polymer constructs.
 /// This is mainly used to produce warnings for feedback in the editor.
 library polymer.src.build.linter;
 
 import 'dart:async';
 import 'dart:convert';
 
 import 'package:barback/barback.dart';
 import 'package:code_transformers/assets.dart';
 import 'package:code_transformers/messages/build_logger.dart';
 import 'package:code_transformers/messages/messages.dart' show Message;
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/dom_parsing.dart';
 import 'package:source_span/source_span.dart';
 
 import 'common.dart';
 import 'utils.dart';
 import 'messages.dart';
 
 /// A linter that checks for common Polymer errors and produces warnings to
 /// show on the editor or the command line. Leaves sources unchanged, but
 /// creates a new asset containing all the warnings.
 class Linter extends Transformer with PolymerTransformer {
   final TransformOptions options;
 
-  /// Only run on .html files.
-  final String allowedExtensions = '.html';
+  Linter(this.options);
 
-  Linter(this.options);
+  isPrimary(AssetId id) =>
+      id.extension == '.html' && options.lint.shouldLint(id.path);
 
   Future apply(Transform transform) {
     var seen = new Set<AssetId>();
     var primary = transform.primaryInput;
     var id = primary.id;
     transform.addOutput(primary); // this phase is analysis only
     seen.add(id);
     bool isEntryPoint = options.isHtmlEntryPoint(id);
 
     var logger = new BuildLogger(transform,
@@ skipping 404 matching lines @@
     upDirCount = segments.length - 2;
   }
   var reachOutPrefix = '../' * upDirCount;
   return USE_POLYMER_HTML.create({'reachOutPrefix': reachOutPrefix});
 }
 
 const List<String> INTERNALLY_DEFINED_ELEMENTS = 
     const ['auto-binding-dart', 'polymer-element'];
 const List<String> AUTO_BINDING_ELEMENTS =
     const ['auto-binding-dart', 'auto-binding'];