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

pkg/polymer/lib/builder.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Common logic to make it easy to run the polymer linter and deploy tool.
  *
  * The functions in this library are designed to make it easier to create
  * `build.dart` files. A `build.dart` file is a Dart script that can be invoked
  * from the command line, but that can also invoked automatically by the Dart
@@ skipping 196 matching lines @@
   if (options == null) {
     print('warning: now that main takes arguments, you need to explicitly pass'
         ' options to deploy(). Running as if no options were passed.');
     options = parseOptions([]);
   }
   if (currentPackage == null) currentPackage = readCurrentPackageFromPubspec();
 
   var transformOptions = new TransformOptions(
       entryPoints: entryPoints,
       directlyIncludeJS: options.directlyIncludeJS,
-      contentSecurityPolicy: options.contentSecurityPolicy);
+      contentSecurityPolicy: options.contentSecurityPolicy,
+      releaseMode: options.releaseMode);
 
   var barbackOptions = new BarbackOptions(
       new PolymerTransformerGroup(transformOptions).phases,
       options.outDir, currentPackage: currentPackage,
       packageDirs: packageDirs);
   return runBarback(barbackOptions)
       .then((_) => print('Done! All files written to "${options.outDir}"'));
 }
 
 
@@ skipping 25 matching lines @@
 
   /** True to use the CSP-compliant JS file. */
   final bool contentSecurityPolicy;
 
   /**
    * True to include the JS script tag directly, without the
    * "packages/browser/dart.js" trampoline.
    */
   final bool directlyIncludeJS;
 
+  /**
+   * Run transformers in release mode. For instance, uses the minified versions
+   * of shadow_dom and custom-elements polyfills.
+   */
+  final bool releaseMode;
+
   CommandLineOptions(this.changedFiles, this.removedFiles, this.clean,
       this.full, this.machineFormat, this.forceDeploy, this.outDir,
-      this.directlyIncludeJS, this.contentSecurityPolicy);
+      this.directlyIncludeJS, this.contentSecurityPolicy,
+      this.releaseMode);
 }
 
 /**
  * Parse command-line arguments and return a [CommandLineOptions] object. The
  * following flags are parsed by this method.
  *
  *   * `--changed file-path`: notify of a file change.
  *   * `--removed file-path`: notify that a file was removed.
  *   * `--clean`: remove temporary artifacts (if any)
  *   * `--full`: build everything, similar to marking every file as changed
@@ skipping 35 matching lines @@
         help: 'Whether to force deploying.')
     ..addOption('out', abbr: 'o', help: 'Directory to generate files into.',
         defaultsTo: 'out')
     ..addFlag('js', help:
         'deploy replaces *.dart scripts with *.dart.js. This flag \n'
         'leaves "packages/browser/dart.js" to do the replacement at runtime.',
         defaultsTo: true)
     ..addFlag('csp', help:
         'replaces *.dart with *.dart.precompiled.js to comply with \n'
         'Content Security Policy restrictions.')
+    ..addFlag('debug', help:
+        'run in debug mode. For example, use the debug versions of the \n'
+        'polyfills (shadow_dom.debug.js and custom-elements.debug.js) \n'
+        'instead of the minified versions.',
+        defaultsTo: false)
     ..addFlag('help', abbr: 'h',
         negatable: false, help: 'Displays this help and exit.');
 
   showUsage() {
     print('Usage: dart build.dart [options]');
     print('\nThese are valid options expected by build.dart:');
     print(parser.getUsage());
   }
 
   var res;
   try {
     res = parser.parse(args);
   } on FormatException catch (e) {
     print(e.message);
     showUsage();
     exit(1);
   }
   if (res['help']) {
     print('A build script that invokes the polymer linter and deploy tools.');
     showUsage();
     exit(0);
   }
   return new CommandLineOptions(res['changed'], res['removed'], res['clean'],
       res['full'], res['machine'], res['deploy'], res['out'], res['js'],
-      res['csp']);
+      res['csp'], !res['debug']);
 }