Add a build filter (only necessary HTML files are emitted) and logic to use .min.js

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

Index: pkg/polymer/lib/src/build/build_filter.dart
diff --git a/pkg/polymer/lib/src/build/build_filter.dart b/pkg/polymer/lib/src/build/build_filter.dart
new file mode 100644
index 0000000000000000000000000000000000000000..61cdd076ae2bd19aa72ffccad23bad5a5d19fe8a
--- /dev/null
+++ b/pkg/polymer/lib/src/build/build_filter.dart
@@ -0,0 +1,44 @@
+// 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.
+
+/**
+ * Final phase of the polymer transformation: removes any files that are not
+ * needed for deployment.
+ */
+library polymer.src.build.build_filter;
+
+import 'dart:async';
+
+import 'package:barback/barback.dart';
+import 'common.dart';
+
+/**
+ * Removes any files not needed for deployment, such as internal build artifacts
+ * and non-entry HTML files.
+ */
+class BuildFilter extends Transformer with PolymerTransformer {
+  final TransformOptions options;
+  BuildFilter(this.options);
+
+  Future<bool> isPrimary(Asset input) => new Future.value(
+      // nothing is filtered in debug mode
+      options.releaseMode &&
+      // may filter non-entry HTML files and internal artifacts
+      (input.id.extension == '.html' || input.id.extension == '.scriptUrls') &&
+      // keep any entry points
+      !options.isHtmlEntryPoint(input.id));
+
+  Future apply(Transform transform) {
+    if (transform.primaryInput.id.extension == '.scriptUrls') {
+      return new Future.value(null);
+    }
+    return readPrimaryAsHtml(transform).then((document) {
+      // Keep .html files that don't use polymer, since the app developer might
+      // have non-polymer entrypoints.
+      if (document.queryAll('polymer-element').isEmpty) {
+        transform.addOutput(transform.primaryInput);
+      }
+    });
+  }
+}