Every place where AllocationMemento is initialized with an

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 7b623b50877d80d371dd2d2dad35d9e9faa38fe9..da25cdf4b855349a1cb641e48ba3975ec76d8826 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -1831,6 +1831,20 @@ HValue* HGraphBuilder::BuildCreateAllocationMemento(HValue* previous_object,
   Handle<Map> alloc_memento_map(
       isolate()->heap()->allocation_memento_map());
   AddStoreMapConstant(alloc_memento, alloc_memento_map);
+
+  // TODO(mvstanton): the code below is turned on to diagnose chromium bug
+  // 284577.
+  Handle<Map> alloc_site_map(isolate()->heap()->allocation_site_map());
+  IfBuilder builder(this);
+  // Read the map
+  HValue* map_field = Add<HLoadNamedField>(alloc_site,
+                                           HObjectAccess::ForMap());
+  HValue* alloc_site_map_value = Add<HConstant>(alloc_site_map);
+  builder.IfNot<HCompareObjectEqAndBranch>(map_field, alloc_site_map_value);
+  builder.Then();
+  AddInstruction(new(zone()) HDebugBreak());
+  builder.End();
+
   HObjectAccess access = HObjectAccess::ForAllocationMementoSite();
   Add<HStoreNamedField>(alloc_memento, access, alloc_site);
   return alloc_memento;