Switch polymer's build.dart to use the new linter. This CL does the following

pkg/polymer/lib/src/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.linter;
 
+import 'dart:io';
 import 'dart:async';
 import 'dart:mirrors';
 import 'dart:convert' show JSON;
 
 import 'package:barback/barback.dart';
 import 'package:html5lib/dom.dart';
 import 'package:html5lib/dom_parsing.dart';
 
 import 'transform/common.dart';
 
 typedef String MessageFormatter(String kind, String message, Span span);
 
 /**
  * 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 {
+class Linter extends Transformer with PolymerTransformer {
+  final TransformOptions options;
+
   /** Only run on .html files. */
   final String allowedExtensions = '.html';
 
   final MessageFormatter _formatter;
 
-  Linter([this._formatter]);
+  Linter(this.options, [this._formatter]);
 
   Future apply(Transform transform) {
     var wrapper = new _LoggerInterceptor(transform, _formatter);
     var seen = new Set<AssetId>();
     var primary = transform.primaryInput;
     var id = primary.id;
     wrapper.addOutput(primary); // this phase is analysis only
     seen.add(id);
     return readPrimaryAsHtml(wrapper).then((document) {
       return _collectElements(document, id, wrapper, seen).then((elements) {
@@ skipping 68 matching lines @@
 
 /** A proxy of [Transform] that returns a different logger. */
 // TODO(sigmund): get rid of this when barback supports a better way to log
 // messages without printing them.
 class _LoggerInterceptor implements Transform, TransformLogger {
   final Transform _original;
   final List<String> _messages = [];
   final MessageFormatter _formatter;
 
   _LoggerInterceptor(this._original, MessageFormatter formatter)
-      : _formatter = formatter == null ? _defaultFormatter : formatter;
+      : _formatter = formatter == null ? consoleFormatter : formatter;
 
   TransformLogger get logger => this;
 
   noSuchMethod(Invocation m) => reflect(_original).delegate(m);
 
   // form TransformLogger:
   void warning(String message, [Span span]) => _write('warning', message, span);
 
   void error(String message, [Span span]) => _write('error', message, span);
 
   void _write(String kind, String message, Span span) {
     _messages.add(_formatter(kind, message, span));
   }
 }
 
 /**
- * Default formatter that generates messages using a format that can be parsed
+ * Formatter that generates messages using a format that can be parsed
  * by tools, such as the Dart Editor, for reporting error messages.
  */
-String _defaultFormatter(String kind, String message, Span span) {
+String jsonFormatter(String kind, String message, Span span) {
   return JSON.encode((span == null)
       ? [{'method': 'warning', 'params': {'message': message}}]
       : [{'method': kind,
           'params': {
             'file': span.sourceUrl,
             'message': message,
             'line': span.start.line + 1,
             'charStart': span.start.offset,
             'charEnd': span.end.offset,
           }}]);
 }
 
+/**
+ * Formatter that generates messages that are easy to read on the console (used
+ * by default).
+ */
+String consoleFormatter(String kind, String message, Span span) {
+  var useColors = stdioType(stdout) == StdioType.TERMINAL;
+  var levelColor = (kind == 'error') ? _RED_COLOR : _MAGENTA_COLOR;
+  var output = new StringBuffer();
+  if (useColors) output.write(levelColor);
+  output..write(kind)..write(' ');
+  if (useColors) output.write(_NO_COLOR);
+  if (span == null) {
+    output.write(message);
+  } else {
+    output.write(span.getLocationMessage(message,
+          useColors: useColors,
+          color: levelColor));
+  }
+  return output.toString();
+}
 
 /**
  * Information needed about other polymer-element tags in order to validate
  * how they are used and extended.
  */
 class _ElementSummary {
   final String tagName;
   final String extendsTag;
   final Span span;
 
@@ skipping 242 matching lines @@
 };
 
 /**
  * Returns true if this is a valid custom element name. See:
  * <https://dvcs.w3.org/hg/webcomponents/raw-file/tip/spec/custom/index.html#dfn-custom-element-name>
  */
 bool _isCustomTag(String name) {
   if (name == null || !name.contains('-')) return false;
   return !_invalidTagNames.containsKey(name);
 }
+
+final String _RED_COLOR = '\u001b[31m';
+final String _MAGENTA_COLOR = '\u001b[35m';
+final String _NO_COLOR = '\u001b[0m';