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

pkg/polymer/lib/transformer.dart

Index: pkg/polymer/lib/transformer.dart
diff --git a/pkg/polymer/lib/transformer.dart b/pkg/polymer/lib/transformer.dart
index 735fac32cd65aa041be3cb41fe445b19fa1041ac..960d9dfec448cc33c71c83089ca3dd504c5f9950 100644
--- a/pkg/polymer/lib/transformer.dart
+++ b/pkg/polymer/lib/transformer.dart
@@ -12,6 +12,7 @@ import 'src/build/build_filter.dart';
 import 'src/build/code_extractor.dart';
 import 'src/build/common.dart';
 import 'src/build/import_inliner.dart';
+import 'src/build/linter.dart';
 import 'src/build/polyfill_injector.dart';
 import 'src/build/script_compactor.dart';
 
@@ -69,6 +70,7 @@ _readEntrypoints(value) {
 
 List<List<Transformer>> _createDeployPhases(TransformOptions options) {
   return [
+    [new Linter(options)],
     [new InlineCodeExtractor(options)],
     [new ObservableTransformer()],
     [new ImportInliner(options)],