Add missing new external to patch file

sdk/lib/_internal/js_runtime/lib/developer_patch.dart

Index: sdk/lib/_internal/js_runtime/lib/developer_patch.dart
diff --git a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
index 07fbcb84f0a5cad78ecd8156a1140c8ffbe3ead7..06d0325bc16b31524335a75700f9a11f470d2034 100644
--- a/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
+++ b/sdk/lib/_internal/js_runtime/lib/developer_patch.dart
@@ -74,6 +74,12 @@ void _reportCompleteEvent(int start, int startCpu, String category, String name,
   // TODO.
 }
 
+@patch
+void _reportFlowEvent(int start, int startCpu, String category, String name,
+    int type, int id, String argumentsAsJson) {
+  // TODO.
+}
+
 @patch
 void _reportInstantEvent(
     int start, String category, String name, String argumentsAsJson) {