Add get_drt.py to test.dart, so that testing browser components updates DumpRenderTree.

tools/testing/dart/test_options.dart

Index: tools/testing/dart/test_options.dart
diff --git a/tools/testing/dart/test_options.dart b/tools/testing/dart/test_options.dart
index e3efee2b836eb3b19fc21124ce973375ad758945..ccd99686a525922c9f91109883abacf06aefa31a 100644
--- a/tools/testing/dart/test_options.dart
+++ b/tools/testing/dart/test_options.dart
@@ -5,6 +5,7 @@
 #library("test_options_parser");
 
 #import("dart:io");
+#import("drt_updater.dart");
 
 List<String> defaultTestSelectors =
     const ['dartc', 'samples', 'standalone', 'corelib', 'co19', 'language',
@@ -456,6 +457,11 @@ Controls how dart code is compiled and executed.
         result.addAll(_expandConfigurations(newConfiguration));
       }
       return result;
+    } else {
+      // All components eventually go through this path, after expansion.
+      if (DumpRenderTreeUpdater.componentRequiresDRT(components)) {
+        DumpRenderTreeUpdater.update();
+      }
     }
 
     // Adjust default timeout based on mode and component.