Add linter by default for polymer's pub-build, also cleans up the linter code.

pkg/polymer/test/build/common.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.
 
 library polymer.test.build.common;
 
 import 'dart:async';
 
 import 'package:barback/barback.dart';
 import 'package:stack_trace/stack_trace.dart';
@@ skipping 13 matching lines @@
  * A helper package provider that has files stored in memory, also wraps
  * [Barback] to simply our tests.
  */
 class TestHelper implements PackageProvider {
   /**
    * Maps from an asset string identifier of the form 'package|path' to the
    * file contents.
    */
   final Map<String, String> files;
   final Iterable<String> packages;
+  final List<String> messages;
+  int messagesSeen = 0;
+  bool errorSeen = false;
 
   Barback barback;
   var errorSubscription;
   var resultSubscription;
+  var logSubscription;
 
   Future<Asset> getAsset(AssetId id) =>
       new Future.value(new Asset.fromString(id, files[idToString(id)]));
-  TestHelper(List<List<Transformer>> transformers, Map<String, String> files)
+
+  TestHelper(List<List<Transformer>> transformers, Map<String, String> files,
+      this.messages)
       : files = files,
         packages = files.keys.map((s) => idFromString(s).package) {
     barback = new Barback(this);
     for (var p in packages) {
       barback.updateTransformers(p, transformers);
     }
+
     errorSubscription = barback.errors.listen((e) {
       var trace = null;
       if (e is Error) trace = e.stackTrace;
       if (trace != null) {
         print(Trace.format(trace));
       }
       fail('error running barback: $e');
     });
+
     resultSubscription = barback.results.listen((result) {
-      expect(result.succeeded, isTrue, reason: "${result.errors}");
+      expect(result.succeeded, !errorSeen, reason: "${result.errors}");
+    });
+
+    logSubscription = barback.log.listen((entry) {
+      if (entry.level == LogLevel.ERROR) errorSeen = true;
+      // We only check messages when an expectation is provided.
+      if (messages == null) return;
+
+      var msg = '${entry.level.name.toLowerCase()}: ${entry.message}';
+      var span = entry.span;
+      var spanInfo = span == null ? '' :
+          ' (${span.sourceUrl} ${span.start.line} ${span.start.column})';
+      expect(messagesSeen, lessThan(messages.length),
+          reason: 'more messages than expected');
+      expect('$msg$spanInfo', messages[messagesSeen++]);
     });
   }
 
   void tearDown() {
     errorSubscription.cancel();
     resultSubscription.cancel();
+    logSubscription.cancel();
   }
 
   /**
    * Tells barback which files have changed, and thus anything that depends on
    * it on should be computed. By default mark all the input files.
    */
   void run([Iterable<String> paths]) {
     if (paths == null) paths = files.keys;
     barback.updateSources(paths.map(idFromString));
   }
 
   Future<String> operator [](String assetString){
     return barback.getAssetById(idFromString(assetString))
         .then((asset) => asset.readAsString());
   }
 
   Future check(String assetIdString, String content) {
     return this[assetIdString].then((value) {
       value = _removeTrailingWhitespace(value);
       content = _removeTrailingWhitespace(content);
       expect(value, content, reason: 'Final output of $assetIdString differs.');
     });
   }
 
   Future checkAll(Map<String, String> files) {
     var futures = [];
     files.forEach((k, v) {
       futures.add(check(k, v));
     });
-    return Future.wait(futures);
+    return Future.wait(futures).then((_) {
+      // We only check messages when an expectation is provided.
+      if (messages == null) return;
+      expect(messages.length, messagesSeen,
+          reason: 'less messages than expected');
+    });
   }
 }
 
 testPhases(String testName, List<List<Transformer>> phases,
-    Map<String, String> inputFiles, Map<String, String> expectedFiles) {
+    Map<String, String> inputFiles, Map<String, String> expectedFiles,
+    [List<String> expectedMessages]) {
   test(testName, () {
-    var helper = new TestHelper(phases, inputFiles)..run();
+    var helper = new TestHelper(phases, inputFiles, expectedMessages)..run();
     return helper.checkAll(expectedFiles).then((_) => helper.tearDown());
   });
 }
 
 // TODO(jmesserly): this is .debug to workaround issue 14720.
 const SHADOW_DOM_TAG =
     '<script src="packages/shadow_dom/shadow_dom.debug.js"></script>\n';
 
 const INTEROP_TAG = '<script src="packages/browser/interop.js"></script>\n';
 const DART_JS_TAG = '<script src="packages/browser/dart.js"></script>';
 
 const CUSTOM_ELEMENT_TAG =
     '<script src="packages/custom_element/custom-elements.debug.js">'
     '</script>\n';