Add map-based read barrier to WeakCell

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index a8cbe9cf153dd91d01a6e20a02f006648f83cb06..cd0457ffff8310d692b9f9c1f3044c2890f38b46 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -9,6 +9,7 @@
 #include "src/heap/objects-visiting.h"
 #include "src/jsregexp.h"
 #include "src/macro-assembler.h"
+#include "src/objects-inl.h"
 #include "src/ostreams.h"
 
 namespace v8 {
@@ -647,7 +648,8 @@ void PropertyCell::PropertyCellVerify() {
 
 void WeakCell::WeakCellVerify() {
   CHECK(IsWeakCell());
-  VerifyObjectField(kValueOffset);
+  Object* value = ValueNoReadBarrier();
+  VerifyPointer(value);
   VerifyObjectField(kNextOffset);
 }