Add mobile safari simulator support in the testing scripts

tools/testing/dart/runtime_configuration.dart

 // Copyright (c) 2014, 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 runtime_configuration;
 
 import 'compiler_configuration.dart' show
     CommandArtifact;
 
 // TODO(ahe): Remove this import, we can precompute all the values required
@@ skipping 18 matching lines @@
       case 'chrome':
       case 'chromeOnAndroid':
       case 'dartium':
       case 'ff':
       case 'firefox':
       case 'ie11':
       case 'ie10':
       case 'ie9':
       case 'opera':
       case 'safari':
+      case 'safarimobilesim':
         // TODO(ahe): Replace this with one or more browser runtimes.
         return new DummyRuntimeConfiguration();
 
       case 'jsshell':
         return new JsshellRuntimeConfiguration();
 
       case 'd8':
         return new D8RuntimeConfiguration();
 
       case 'none':
@@ skipping 171 matching lines @@
 class DummyRuntimeConfiguration extends DartVmRuntimeConfiguration {
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     throw "Unimplemented runtime '$runtimeType'";
   }
 }