Use browser_controller instead of selenium in test scripts, by default.

tools/testing/dart/test_suite.dart

Index: tools/testing/dart/test_suite.dart
diff --git a/tools/testing/dart/test_suite.dart b/tools/testing/dart/test_suite.dart
index c078eb08cb46c261a100e31ce83807fc6615b212..1c9fdeadc8b8b8a83c8cc752359225900fd3004c 100644
--- a/tools/testing/dart/test_suite.dart
+++ b/tools/testing/dart/test_suite.dart
@@ -1093,7 +1093,26 @@ class StandardTestSuite extends TestSuite {
 
         List<String> args = <String>[];
 
-        if (configuration['use_browser_controller']) {
+        if (runtime == "drt") {
+          var dartFlags = [];
+          var contentShellOptions = [];
+
+          contentShellOptions.add('--no-timeout');
+          contentShellOptions.add('--dump-render-tree');
+
+          if (compiler == 'none' || compiler == 'dart2dart') {
+            dartFlags.add('--ignore-unrecognized-flags');
+            if (configuration["checked"]) {
+              dartFlags.add('--enable_asserts');
+              dartFlags.add("--enable_type_checks");
+            }
+            dartFlags.addAll(vmOptions);
+          }
+
+          commandSet.add(CommandBuilder.instance.getContentShellCommand(
+              contentShellFilename, fullHtmlPath, contentShellOptions,
+              dartFlags, configurationDir));
+        } else if (configuration['use_browser_controller']) {
           // This command is not actually run, it is used for reproducing
           // the failure.
           args = ['tools/testing/dart/launch_browser.dart',
@@ -1102,7 +1121,8 @@ class StandardTestSuite extends TestSuite {
           commandSet.add(CommandBuilder.instance.getBrowserTestCommand(
               runtime, fullHtmlPath, TestUtils.dartTestExecutable.toString(),
               args, configurationDir, checkedMode: configuration['checked']));
-        } else if (TestUtils.usesWebDriver(runtime)) {
+        } else {
+          assert(TestUtils.usesWebDriver(runtime));
           args = [
               dartDir.append('tools/testing/run_selenium.py').toNativePath(),
               '--browser=$runtime',
@@ -1119,27 +1139,6 @@ class StandardTestSuite extends TestSuite {
           }
           commandSet.add(CommandBuilder.instance.getSeleniumTestCommand(
                   runtime, fullHtmlPath, 'python', args, configurationDir));
-        } else {
-          assert(runtime == "drt");
-
-          var dartFlags = [];
-          var contentShellOptions = [];
-
-          contentShellOptions.add('--no-timeout');
-          contentShellOptions.add('--dump-render-tree');
-
-          if (compiler == 'none' || compiler == 'dart2dart') {
-            dartFlags.add('--ignore-unrecognized-flags');
-            if (configuration["checked"]) {
-              dartFlags.add('--enable_asserts');
-              dartFlags.add("--enable_type_checks");
-            }
-            dartFlags.addAll(vmOptions);
-          }
-
-          commandSet.add(CommandBuilder.instance.getContentShellCommand(
-              contentShellFilename, fullHtmlPath, contentShellOptions,
-              dartFlags, configurationDir));
         }
 
         // Create BrowserTestCase and queue it.