Polymer transformer logs now show on the frontend for pub serve.

pkg/polymer/lib/transformer.dart

 // Copyright (c) 2013, 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.
 
 /// Transfomer used for pub-serve and pub-deploy.
 library polymer.transformer;
 
 import 'package:barback/barback.dart';
 import 'package:observe/transformer.dart';
 import 'package:path/path.dart' as path;
 
 import 'src/build/build_filter.dart';
 import 'src/build/common.dart';
 import 'src/build/import_inliner.dart';
 import 'src/build/linter.dart';
+import 'src/build/build_log_combiner.dart';
 import 'src/build/polyfill_injector.dart';
 import 'src/build/script_compactor.dart';
 
 /// The Polymer transformer, which internally runs several phases that will:
 ///   * Extract inlined script tags into their separate files
 ///   * Apply the observable transformer on every Dart script.
 ///   * Inline imported html files
 ///   * Combine scripts from multiple files into a single script tag
 ///   * Inject extra polyfills needed to run on all browsers.
 ///
 /// At the end of these phases, this tranformer produces a single entrypoint
 /// HTML file with a single Dart script that can later be compiled with dart2js.
 class PolymerTransformerGroup implements TransformerGroup {
   final Iterable<Iterable> phases;
 
   PolymerTransformerGroup(TransformOptions options)
       : phases = createDeployPhases(options);
 
   PolymerTransformerGroup.asPlugin(BarbackSettings settings)
       : this(_parseSettings(settings));
 }
 
 TransformOptions _parseSettings(BarbackSettings settings) {
   var args = settings.configuration;
   bool releaseMode = settings.mode == BarbackMode.RELEASE;
   bool jsOption = args['js'];
   bool csp = args['csp'] == true; // defaults to false
   bool lint = args['lint'] != false; // defaults to true
+  bool injectBuildLogs =
+      !releaseMode && args['inject_build_logs_in_output'] != false;
   return new TransformOptions(
       entryPoints: _readEntrypoints(args['entry_points']),
       inlineStylesheets: _readInlineStylesheets(args['inline_stylesheets']),
       directlyIncludeJS: jsOption == null ? releaseMode : jsOption,
       contentSecurityPolicy: csp,
       releaseMode: releaseMode,
-      lint: lint);
+      lint: lint,
+      injectBuildLogsInOutput: injectBuildLogs);
 }
 
 _readEntrypoints(value) {
   if (value == null) return null;
   var entryPoints = [];
   bool error;
   if (value is List) {
     entryPoints = value;
     error = value.any((e) => e is! String);
   } else if (value is String) {
@@ skipping 51 matching lines @@
     TransformOptions options, {String sdkDir}) {
   // TODO(sigmund): this should be done differently. We should lint everything
   // that is reachable and have the option to lint the rest (similar to how
   // dart2js can analyze reachable code or entire libraries).
   var phases = options.lint ? [[new Linter(options)]] : [];
   return phases..addAll([
     [new ImportInliner(options)],
     [new ObservableTransformer()],
     [new ScriptCompactor(options, sdkDir: sdkDir)],
     [new PolyfillInjector(options)],
-    [new BuildFilter(options)]
+    [new BuildFilter(options)],
+    [new BuildLogCombiner(options)],
   ]);
 }
 
-final RegExp _PACKAGE_PATH_REGEX = new RegExp(r'packages\/([^\/]+)\/(.*)');
+final RegExp _PACKAGE_PATH_REGEX = new RegExp(r'packages\/([^\/]+)\/(.*)');