Only fetch the Observatory URL in debug mode.

lib/src/runner/browser/content_shell.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.runner.browser.content_shell;
 
 import 'dart:async';
 import 'dart:io';
 
 import '../../utils.dart';
 import '../application_exception.dart';
 import 'browser.dart';
 
 final _observatoryRegExp = new RegExp(r"^Observatory listening on ([^ ]+)");
 
 /// A class for running an instance of the Dartium content shell.
 ///
 /// Most of the communication with the browser is expected to happen via HTTP,
 /// so this exposes a bare-bones API. The browser starts as soon as the class is
 /// constructed, and is killed when [close] is called.
 ///
 /// Any errors starting or running the process are reported through [onExit].
 class ContentShell extends Browser {
   final name = "Content Shell";
 
   final Future<Uri> observatoryUrl;
 
-  factory ContentShell(url, {String executable}) {
+  factory ContentShell(url, {String executable, bool debug: false}) {
     var completer = new Completer.sync();
     return new ContentShell._(() async {
       if (executable == null) executable = _defaultExecutable();
 
       var process = await Process.start(
           executable, ["--dump-render-tree", url.toString()],
           environment: {"DART_FLAGS": "--checked"});
 
-      // The first observatory URL emitted is for the empty start page; the
-      // second is actually for the host page.
-      completer.complete(lineSplitter.bind(process.stdout).map((line) {
-        var match = _observatoryRegExp.firstMatch(line);
-        if (match == null) return null;
-        return Uri.parse(match[1]);
-      }).where((uri) => uri != null).first);
+      if (debug) {
+        completer.complete(lineSplitter.bind(process.stdout).map((line) {
+          var match = _observatoryRegExp.firstMatch(line);
+          if (match == null) return null;
+          return Uri.parse(match[1]);
+        }).where((uri) => uri != null).first);
+      } else {
+        completer.complete(null);
+      }
 
       lineSplitter.bind(process.stderr).listen((line) {
         if (line != "[dartToStderr]: Dartium build has expired") return;
 
         // TODO(nweiz): link to dartlang.org once it has download links for
         // content shell
         // (https://github.com/dart-lang/www.dartlang.org/issues/1164).
         throw new ApplicationException(
             "You're using an expired content_shell. Upgrade to the latest "
                 "version:\n"
             "http://gsdview.appspot.com/dart-archive/channels/stable/release/"
                 "latest/dartium/");
       });
 
       return process;
     }, completer.future);
   }
 
   ContentShell._(Future<Process> startBrowser(), this.observatoryUrl)
       : super(startBrowser);
 
   /// Return the default executable for the current operating system.
   static String _defaultExecutable() =>
       Platform.isWindows ? "content_shell.exe" : "content_shell";
 }