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

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

Index: pkg/polymer/lib/src/build/common.dart
diff --git a/pkg/polymer/lib/src/build/common.dart b/pkg/polymer/lib/src/build/common.dart
index 672456111f9382562b05b75388487aa339dc2bc5..1bb43797b6ece80ce5b19f6acdf69193809a4209 100644
--- a/pkg/polymer/lib/src/build/common.dart
+++ b/pkg/polymer/lib/src/build/common.dart
@@ -62,8 +62,14 @@ class TransformOptions {
    */
   final bool directlyIncludeJS;
 
+  /**
+   * Run transformers to create a releasable app. For example, include the
+   * minified versions of the polyfills rather than the debug versions.
+   */
+  final bool releaseMode;
+
   TransformOptions({entryPoints, this.contentSecurityPolicy: false,
-      this.directlyIncludeJS: true})
+      this.directlyIncludeJS: true, this.releaseMode: true})
       : entryPoints = entryPoints == null ? null
           : entryPoints.map(_systemToAssetPath).toList();