Expose the Observatory URL when debugging.

lib/src/backend/test_platform.dart

 // Copyright (c) 2015, 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.
 
 library test.backend.test_platform;
 
 // TODO(nweiz): support pluggable platforms.
 /// An enum of all platforms on which tests can run.
 class TestPlatform {
   // When adding new platforms, be sure to update the baseline and derived
   // variable tests in test/backend/platform_selector/evaluate_test.
 
   /// The command-line Dart VM.
   static const TestPlatform vm =
       const TestPlatform._("VM", "vm", isDartVM: true);
 
   /// Dartium.
   static const TestPlatform dartium = const TestPlatform._("Dartium", "dartium",
       isBrowser: true, isBlink: true, isDartVM: true);
 
   /// Dartium content shell.
   static const TestPlatform contentShell = const TestPlatform._(
       "Dartium Content Shell", "content-shell",
-      isBrowser: true, isBlink: true, isDartVM: true);
+      isBrowser: true, isBlink: true, isDartVM: true, isHeadless: true);
 
   /// Google Chrome.
   static const TestPlatform chrome = const TestPlatform._("Chrome", "chrome",
       isBrowser: true, isJS: true, isBlink: true);
 
   /// PhantomJS.
   static const TestPlatform phantomJS = const TestPlatform._(
       "PhantomJS", "phantomjs",
-      isBrowser: true, isJS: true, isBlink: true);
+      isBrowser: true, isJS: true, isBlink: true, isHeadless: true);
 
   /// Mozilla Firefox.
   static const TestPlatform firefox = const TestPlatform._("Firefox", "firefox",
       isBrowser: true, isJS: true);
 
   /// Apple Safari.
   static const TestPlatform safari = const TestPlatform._("Safari", "safari",
       isBrowser: true, isJS: true);
 
   /// Microsoft Internet Explorer.
@@ skipping 31 matching lines @@
 
   /// Whether this platform is a browser.
   final bool isBrowser;
 
   /// Whether this platform runs Dart compiled to JavaScript.
   final bool isJS;
 
   /// Whether this platform uses the Blink rendering engine.
   final bool isBlink;
 
+  /// Whether this platform has no visible window.
+  final bool isHeadless;
+
   const TestPlatform._(this.name, this.identifier, {this.isDartVM: false,
-      this.isBrowser: false, this.isJS: false, this.isBlink: false});
+      this.isBrowser: false, this.isJS: false, this.isBlink: false,
+      this.isHeadless: false});
 
   String toString() => name;
 }