update to polymer js 0.5.1

pkg/polymer/lib/builder.dart

Index: pkg/polymer/lib/builder.dart
diff --git a/pkg/polymer/lib/builder.dart b/pkg/polymer/lib/builder.dart
index 1ddefc8cb4517a4a4668d166629e45fc38d25fd5..5419dd259dba8c0213ae078402bf6daaf26d66cc 100644
--- a/pkg/polymer/lib/builder.dart
+++ b/pkg/polymer/lib/builder.dart
@@ -297,7 +297,7 @@ CommandLineOptions parseOptions([List<String> args]) {
         'Content Security Policy restrictions.')
     ..addFlag('debug', help:
         'run in debug mode. For example, use the debug polyfill \n'
-        'web_components/platform.concat.js instead of the minified one.\n',
+        'web_components/webcomponents.js instead of the minified one.\n',
         defaultsTo: false)
     ..addFlag('help', abbr: 'h',
         negatable: false, help: 'Displays this help and exit.');