Update dart2js diagnostics to prepare for filtering.

tests/compiler/dart2js/exit_code_test.dart

Index: tests/compiler/dart2js/exit_code_test.dart
diff --git a/tests/compiler/dart2js/exit_code_test.dart b/tests/compiler/dart2js/exit_code_test.dart
index b0afedd45475a7938fd91afee1d70804d5d77171..fd5c38f8331c22118650efb8a2fa10c827e2af28 100644
--- a/tests/compiler/dart2js/exit_code_test.dart
+++ b/tests/compiler/dart2js/exit_code_test.dart
@@ -88,8 +88,8 @@ class TestCompiler extends apiimpl.Compiler {
         break;
       case 'warning':
         onTest(testMarker, testType);
-        reportWarningCode(CURRENT_ELEMENT_SPANNABLE,
-                          MessageKind.GENERIC, {'text': marker});
+        reportWarning(CURRENT_ELEMENT_SPANNABLE,
+                      MessageKind.GENERIC, {'text': marker});
         break;
       case 'error':
         onTest(testMarker, testType);