Only fetch the Observatory URL in debug mode.

lib/src/runner/browser/server.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.server;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 356 matching lines @@
     var manager = _browserManagers[platform];
     if (manager != null) return Result.release(manager);
 
     var completer = new Completer.sync();
     var path = _webSocketHandler.create(webSocketHandler(completer.complete));
     var webSocketUrl = url.replace(scheme: 'ws').resolve(path);
     var hostUrl = (_config.pubServeUrl == null ? url : _config.pubServeUrl)
         .resolve('packages/test/src/runner/browser/static/index.html')
         .replace(queryParameters: {'managerUrl': webSocketUrl.toString()});
 
-    var future = BrowserManager.start(platform, hostUrl, completer.future);
+    var future = BrowserManager.start(platform, hostUrl, completer.future,
+        debug: _config.pauseAfterLoad);
 
     // Capture errors and release them later to avoid Zone issues. This call to
     // [_browserManagerFor] is running in a different [LoadSuite] than future
     // calls, which means they're also running in different error zones so
     // errors can't be freely passed between them. Storing the error or value as
     // an explicit [Result] fixes that.
     _browserManagers[platform] = Result.capture(future);
 
     return future;
   }
@@ skipping 17 matching lines @@
       await Future.wait(futures);
 
       if (_config.pubServeUrl == null) {
         new Directory(_compiledDir).deleteSync(recursive: true);
       } else {
         _http.close();
       }
     });
   }
 }