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

pkg/polymer/lib/transformer.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.
 
 /** Transfomer used for pub-serve and pub-deploy. */
 library polymer.transformer;
 
 import 'package:barback/barback.dart';
 import 'package:observe/transformer.dart';
+
+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/polyfill_injector.dart';
 import 'src/build/script_compactor.dart';
-import 'src/build/polyfill_injector.dart';
-import 'src/build/common.dart';
 
 /**
  * The Polymer transformer, which internally runs several phases that will:
  *   * Extract inlined script tags into their separate files
  *   * Apply the observable transformer on every Dart script.
  *   * Inline imported html files
  *   * Combine scripts from multiple files into a single script tag
  *   * Inject extra polyfills needed to run on all browsers.
  *
  * At the end of these phases, this tranformer produces a single entrypoint HTML
  * file with a single Dart script that can later be compiled with dart2js.
  */
 class PolymerTransformerGroup implements TransformerGroup {
   final Iterable<Iterable> phases;
 
   PolymerTransformerGroup(TransformOptions options)
       : phases = _createDeployPhases(options);
 
   PolymerTransformerGroup.asPlugin(BarbackSettings settings)
       : this(_parseSettings(settings));
 }
 
 TransformOptions _parseSettings(BarbackSettings settings) {
   var args = settings.configuration;
-  bool release = settings.mode == BarbackMode.RELEASE;
+  bool releaseMode = settings.mode == BarbackMode.RELEASE;
   bool jsOption = args['js'];
   bool csp = args['csp'] == true; // defaults to false
   return new TransformOptions(
       entryPoints: _readEntrypoints(args['entry_points']),
-      directlyIncludeJS: jsOption == null ? release : jsOption,
-      contentSecurityPolicy: csp);
+      directlyIncludeJS: jsOption == null ? releaseMode : jsOption,
+      contentSecurityPolicy: csp,
+      releaseMode: releaseMode);
 }
 
 _readEntrypoints(value) {
   if (value == null) return null;
   var entryPoints = [];
   bool error;
   if (value is List) {
     entryPoints = value;
     error = value.any((e) => e is! String);
   } else if (value is String) {
     entryPoints = [value];
     error = false;
   } else {
     error = true;
   }
   if (error) {
     print('Invalid value for "entry_points" in the polymer transformer.');
   }
   return entryPoints;
 }
 
 List<List<Transformer>> _createDeployPhases(TransformOptions options) {
   return [
     [new InlineCodeExtractor(options)],
     [new ObservableTransformer()],
     [new ImportInliner(options)],
     [new ScriptCompactor(options)],
-    [new PolyfillInjector(options)]
+    [new PolyfillInjector(options)],
+    [new BuildFilter(options)]
   ];
 }