Delay Firefox browser startup in test scripts, to flatten load.

tools/testing/dart/browser_controller.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.
 library browser;
 
 import "dart:async";
 import "dart:convert" show LineSplitter, UTF8, JSON;
 import "dart:core";
 import "dart:io";
 import "dart:math" show max, min;
@@ skipping 749 matching lines @@
         };
         var args = [
           "-profile",
           "${userDir.path}",
           "-no-remote",
           "-new-instance",
           url
         ];
         var environment = new Map<String, String>.from(Platform.environment);
         environment["MOZ_CRASHREPORTER_DISABLE"] = "1";
-        return startBrowserProcess(_binary, args, environment: environment);
+        // TODO(26060): Remove delay when dart2js stops hanging under load.
+        return new Future.delayed(new Duration(seconds: 10)).then((_) {

[Siggi Cherem (dart-lang), 2016/04/25 18:21:41]

since this is only causing issues in windows, can we conditionally perform the
delay only there?

[Bill Hesse, 2016/04/26 19:25:08]

We only test on linux and windows, and this delay is not very significant at
all, and this object does not have information about which platform it is
running on.  So I prefer not to do this.  If we need to, we can query the
Platform.isWindows value from dart:io Platform, so it is doable.

+          return startBrowserProcess(_binary, args, environment: environment);
+        });
       });
     }).catchError((e) {
       _logEvent("Running $_binary --version failed with $e");
       return false;
     });
   }
 
   String toString() => "Firefox";
 }
 
@@ skipping 1001 matching lines @@
     </div>
     <div id="embedded_iframe_div" class="test box">
       <iframe style="width:100%;height:100%;" id="embedded_iframe"></iframe>
     </div>
   </body>
 </html>
 """;
     return driverContent;
   }
 }