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

pkg/polymer/test/build/log_injector_test.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.
+
+import 'dart:async';
+import 'dart:html';
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import 'package:polymer/src/build/log_injector.dart';
+
+
+main() {
+
+  useHtmlConfiguration();
+
+  setUp(() => new LogInjector().injectLogs(
+      '''[
+          {"level": "Info", "message": "foo"},
+          {"level": "Warning", "message": "bar"},
+          {"level": "Error", "message": "baz"}
+      ]'''
+  ));
+
+  test('can inject a functioning log widget', () {
+    var logsElement = document.querySelector(".build-logs");
+    expect(logsElement, isNotNull);
+
+    var menuElements = logsElement.querySelectorAll(".menu > div");
+    expect(menuElements.length, 3);
+    var contentElements = logsElement.querySelectorAll(".content > div");
+    expect(contentElements.length, 3);
+
+    var expectedClasses = ['info', 'warning', 'error'];
+
+    // Check initial setup.
+    for (var i = 0; i < menuElements.length; ++i) {
+      expect(menuElements[i].classes.contains(expectedClasses[i]), true);
+      expect(menuElements[i].classes.contains('active'), false);
+      expect(contentElements[i].classes.contains(expectedClasses[i]), true);
+      expect(contentElements[i].classes.contains('active'), false);
+      expect(contentElements[i].querySelectorAll('.log').length, 1);
+    }
+
+    // Test clicking each of the tabs.
+    for (var i = 0; i < menuElements.length; ++i) {
+      menuElements[i].click();
+      for (var j = 0; j < menuElements.length; ++j) {
+        expect(menuElements[j].classes.contains('active'), j == i);
+        expect(contentElements[j].classes.contains('active'), j == i);
+      }
+    }
+
+    // Test toggling same tab.
+    expect(menuElements[2].classes.contains('active'), true);
+    menuElements[2].click();
+    expect(menuElements[2].classes.contains('active'), false);
+    expect(contentElements[2].classes.contains('active'), false);
+  });
+}