Add a browser configuration to avoid repeating (runtime == 'ff' || runtime == 'ie' || ...).

dart/tools/testing/dart/test_options.dart

Index: dart/tools/testing/dart/test_options.dart
===================================================================
--- dart/tools/testing/dart/test_options.dart	(revision 8032)
+++ dart/tools/testing/dart/test_options.dart	(working copy)
@@ -7,6 +7,7 @@
 #import("dart:io");
 #import("dart:builtin");
 #import("drt_updater.dart");
+#import("test_suite.dart");
 
 List<String> defaultTestSelectors =
     const ['dartc', 'samples', 'standalone', 'corelib', 'co19', 'language',
@@ -466,10 +467,15 @@
     configuration['unchecked'] = !configuration['checked'];
     configuration['host_unchecked'] = !configuration['host_checked'];
 
-    if (configuration['runtime'] == 'firefox') {
+    String runtime = configuration['runtime'];
+    if (runtime == 'firefox') {
       configuration['runtime'] == 'ff';
     }
 
+    if (TestUtils.isBrowserRuntime(runtime)) {
+      configuration['browser'] = true;
+    }
+
     // Expand the test selectors into a suite name and a simple
     // regular expressions to be used on the full path of a test file
     // in that test suite. If no selectors are explicitly given use