[ic] Use validity cells to protect keyed element stores against object's prototype chain modificati…

src/objects-debug.cc

Index: src/objects-debug.cc
diff --git a/src/objects-debug.cc b/src/objects-debug.cc
index db50cfba75b5e5f64550075a8c0afa407ea8d8d0..ca23f201c8c31454ae83b61f7b70a51abb2efd5f 100644
--- a/src/objects-debug.cc
+++ b/src/objects-debug.cc
@@ -1078,6 +1078,12 @@ void PrototypeInfo::PrototypeInfoVerify() {
   CHECK(validity_cell()->IsCell() || validity_cell()->IsSmi());
 }
 
+void Tuple2::Tuple2Verify() {
+  CHECK(IsTuple2());
+  VerifyObjectField(kValue1Offset);
+  VerifyObjectField(kValue2Offset);
+}
+
 void Tuple3::Tuple3Verify() {
   CHECK(IsTuple3());
   VerifyObjectField(kValue1Offset);