delete debug only files from output in release mode

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

Index: pkg/polymer/lib/src/build/remove_sourcemap_comment.dart
diff --git a/pkg/polymer/lib/src/build/remove_sourcemap_comment.dart b/pkg/polymer/lib/src/build/remove_sourcemap_comment.dart
new file mode 100644
index 0000000000000000000000000000000000000000..cc106db62588622ad64a44c9655a86e82403b560
--- /dev/null
+++ b/pkg/polymer/lib/src/build/remove_sourcemap_comment.dart
@@ -0,0 +1,32 @@
+// Copyright (c) 2014, 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.
+
+/// Transformer that removes any sourcemap comments from javascript files.
+library web_components.src.remove_sourcemap_comment;
+
+import 'dart:async';
+import 'package:barback/barback.dart';
+
+/// Transformer that removes any sourcemap comments from javascript files.
+/// Comments should be on their own line in the form: //# sourceMappingURL=*.map
+class RemoveSourcemapComment extends Transformer {
+  BarbackSettings settings;
+
+  RemoveSourcemapComment.asPlugin(this.settings);
+
+  /// Only apply to files in release mode.
+  isPrimary(_) => settings.mode == BarbackMode.RELEASE;
+
+  apply(Transform transform) {
+    var id = transform.primaryInput.id;
+    return transform.readInputAsString(id).then((file) {
+      if (file.contains(_SOURCE_MAP_COMMENT)) {
+        transform.addOutput(new Asset.fromString(
+            id, file.replaceAll(_SOURCE_MAP_COMMENT, '')));
+      }
+    });
+  }
+}
+
+final RegExp _SOURCE_MAP_COMMENT = new RegExp(r'\n\s*\/\/# sourceMappingURL.*');