Every place where AllocationMemento is initialized with an

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index 24e4039422cc8ae010b17c9f700f32061d2cd204..108cfb373e71674f0a976e49d981a959e1be6051 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -4310,6 +4310,10 @@ MaybeObject* Heap::AllocateWithAllocationSite(Map* map, AllocationSpace space,
   AllocationMemento* alloc_memento = reinterpret_cast<AllocationMemento*>(
       reinterpret_cast<Address>(result) + map->instance_size());
   alloc_memento->set_map_no_write_barrier(allocation_memento_map());
+
+  // TODO(mvstanton): To diagnose bug 284577, some extra checks
+  CHECK(allocation_site->map() == allocation_site_map());
+
   alloc_memento->set_allocation_site(*allocation_site, SKIP_WRITE_BARRIER);
   return result;
 }
@@ -5053,6 +5057,10 @@ MaybeObject* Heap::CopyJSObjectWithAllocationSite(
       AllocationMemento* alloc_memento;
       if (maybe_alloc_memento->To(&alloc_memento)) {
         alloc_memento->set_map_no_write_barrier(allocation_memento_map());
+
+        // TODO(mvstanton): To diagnose bug 284577, some extra checks
+        CHECK(site->map() == allocation_site_map());
+
         alloc_memento->set_allocation_site(site, SKIP_WRITE_BARRIER);
       }
     }
@@ -5075,6 +5083,10 @@ MaybeObject* Heap::CopyJSObjectWithAllocationSite(
     AllocationMemento* alloc_memento = reinterpret_cast<AllocationMemento*>(
         reinterpret_cast<Address>(clone) + object_size);
     alloc_memento->set_map_no_write_barrier(allocation_memento_map());
+
+    // TODO(mvstanton): To diagnose bug 284577, some extra checks
+    CHECK(site->map() == allocation_site_map());
+
     alloc_memento->set_allocation_site(site, SKIP_WRITE_BARRIER);
   }