Control whether pub build and serve minify or not.

sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart

Index: sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart b/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
index 777ee8ff171e7714acdf0465e1873d4aefe47d7f..293ac2fc3b9cb53c54cbbde4593dc91ea91e904f 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/dart2js_transformer.dart
@@ -26,12 +26,16 @@ import '../package_graph.dart';
 class Dart2JSTransformer extends Transformer {
   final PackageGraph _graph;
 
+  /// Whether the JavaScript output should be minified.
+  final bool _minify;
+
   /// The [AssetId]s the transformer has discovered so far. Used by pub build
   /// to determine where to copy the JS bootstrap files.
   // TODO(rnystrom): Do something cleaner for this, or eliminate those files.
   final entrypoints = new Set<AssetId>();
 
-  Dart2JSTransformer(this._graph);
+  Dart2JSTransformer(this._graph, {bool minify})
+      : _minify = minify == true ? true : false;
 
   /// Only ".dart" files within "web/" are processed.
   Future<bool> isPrimary(Asset asset) {
@@ -77,6 +81,7 @@ class Dart2JSTransformer extends Transformer {
       // path so they can understand them.
       return dart.compile(entrypoint,
           packageRoot: packageRoot,
+          minify: _minify,
           inputProvider: provider.readStringFromUri,
           diagnosticHandler: provider.handleDiagnostic).then((js) {
         var id = transform.primaryInput.id.changeExtension(".dart.js");