Blink GC plugin: Require that fields are actually traced by the visitor and identify tracing of dep…

tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp

Index: tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp
diff --git a/tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp b/tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp
index 475d40f7d9b72533c32d1c51eb15c753f75eddee..977951058f77059fe8a93278d615cc6be3937aa9 100644
--- a/tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp
+++ b/tools/clang/blink_gc_plugin/tests/fields_require_tracing.cpp
@@ -7,7 +7,7 @@
 namespace blink {
 
 void PartObject::trace(Visitor* visitor) {
-    // Missing visitor->trace(m_obj1);
+    m_obj1->trace(visitor); // Don't allow direct tracing.
     visitor->trace(m_obj2);
     // Missing visitor->trace(m_obj3);
 }