Introduce --zap-cpp-pointers (off by default)

src/heap/heap-inl.h

Index: src/heap/heap-inl.h
diff --git a/src/heap/heap-inl.h b/src/heap/heap-inl.h
index 1ed19107f01b35b0e9549e174fa3a985c3d29622..6594c33bd19d558ef17a7dbf598b10fa94d05672 100644
--- a/src/heap/heap-inl.h
+++ b/src/heap/heap-inl.h
@@ -305,6 +305,13 @@ AllocationResult Heap::AllocateRaw(int size_in_bytes, AllocationSpace space,
   }
   isolate_->counters()->objs_since_last_full()->Increment();
   isolate_->counters()->objs_since_last_young()->Increment();
+
+// TODO(jkummerow): Handlify more of heap.cc to maintain the rule that
+// "there are no raw pointers anywhere on the stack when an allocation
+// is happening", and then remove the ZapHeapPointersInCppFrames() call
+// from CALL_HEAP_FUNCTION and instead enable it here.
+
+// if (FLAG_zap_cpp_pointers) ZapHeapPointersInCppFrames(isolate_);
 #endif
 
   bool large_object = size_in_bytes > kMaxRegularHeapObjectSize;