Control whether pub build and serve minify or not.

sdk/lib/_internal/pub/lib/src/command/serve.dart

Index: sdk/lib/_internal/pub/lib/src/command/serve.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/serve.dart b/sdk/lib/_internal/pub/lib/src/command/serve.dart
index 3224f49eb79f1e06fb7167cf16db4d130986477c..0d7adfc361ea8e652b9718fb0258b73913665067 100644
--- a/sdk/lib/_internal/pub/lib/src/command/serve.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/serve.dart
@@ -31,6 +31,9 @@ class ServeCommand extends PubCommand {
   /// `true` if Dart entrypoints should be compiled to JavaScript.
   bool get useDart2JS => commandOptions['dart2js'];
 
+  /// `true` if generated JavaScript should be minified.
+  bool get minify => commandOptions['minify'];
+
   ServeCommand() {
     commandParser.addOption('port', defaultsTo: '8080',
         help: 'The port to listen on.');
@@ -45,6 +48,9 @@ class ServeCommand extends PubCommand {
 
     commandParser.addFlag('dart2js', defaultsTo: true,
         help: 'Compile Dart to JavaScript.');
+
+    commandParser.addFlag('minify', defaultsTo: false,
+        help: 'Minify generated JavaScript.');
   }
 
   Future onRun() {
@@ -64,7 +70,7 @@ class ServeCommand extends PubCommand {
       var builtInTransformers = null;
       if (useDart2JS) {
         builtInTransformers = [
-          new Dart2JSTransformer(graph),
+          new Dart2JSTransformer(graph, minify: minify),
           new DartForwardingTransformer()
         ];
       }