Check Member<T> validity for stack allocated objects.

tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt

Index: tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt
diff --git a/tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt b/tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt
index 6aada915e54575ef80b4b96df2b8e2ac7d0aa507..9d5f2388dc8b3d140c87d7b6cbbef915658db8ff 100644
--- a/tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt
+++ b/tools/clang/blink_gc_plugin/tests/member_in_offheap_class.txt
@@ -5,4 +5,13 @@ class OffHeapObject {
 ./member_in_offheap_class.h:18:5: note: [blink-gc] Member field 'm_obj' in unmanaged class declared here:
     Member<HeapObject> m_obj; // Must not contain Member.
     ^
-1 warning generated.
+./member_in_offheap_class.h:22:1: warning: [blink-gc] Class 'StackObject' contains invalid fields.
+class StackObject {
+^
+./member_in_offheap_class.h:26:5: note: [blink-gc] Member field 'm_memberOff' to non-GC managed class declared here:
+    Member<OffHeapObject> m_memberOff; // NOT OK
+    ^
+./member_in_offheap_class.h:27:5: note: [blink-gc] Member field 'm_heapVectorMemberOff' to non-GC managed class declared here:
+    HeapVector<Member<OffHeapObject>> m_heapVectorMemberOff; // NOT OK
+    ^
+2 warnings generated.