Temporarily double timeout to test Mac fullbots timing out with DRT

tools/testing/dart/test_runner.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Classes and methods for executing tests.
  *
  * This module includes:
  * - Managing parallel execution of tests, including timeout checks.
  * - Evaluating the output of each test as pass/fail/crash/timeout.
@@ skipping 10 matching lines @@
 import 'dependency_graph.dart' as dgraph;
 import "browser_controller.dart";
 import "path.dart";
 import "status_file_parser.dart";
 import "test_progress.dart";
 import "test_suite.dart";
 import "utils.dart";
 import 'record_and_replay.dart';
 
 const int CRASHING_BROWSER_EXITCODE = -10;
-const int SLOW_TIMEOUT_MULTIPLIER = 4;
+const int SLOW_TIMEOUT_MULTIPLIER = 8;
 
 const MESSAGE_CANNOT_OPEN_DISPLAY = 'Gtk-WARNING **: cannot open display';
 const MESSAGE_FAILED_TO_RUN_COMMAND = 'Failed to run command. return code=1';
 
 typedef void TestCaseEvent(TestCase testCase);
 typedef void ExitCodeEvent(int exitCode);
 typedef void EnqueueMoreWork(ProcessQueue queue);
 
 // Some IO tests use these variables and get confused if the host environment
 // variables are inherited so they are excluded.
@@ skipping 2924 matching lines @@
     }
   }
 
   void eventAllTestsDone() {
     for (var listener in _eventListener) {
       listener.allDone();
     }
     _allDone();
   }
 }