Merge V8 5.2.361.47  DO NOT MERGE

https://chromium.googlesource.com/v8/v8/+/5.2.361.47

FPIIM-449

Change-Id: Ibec421b85a9b88cb3a432ada642e469fe7e78346
(cherry picked from commit bcf72ee8e3b26f1d0726869c7ddb3921c68b09a8)
diff --git a/src/snapshot/serializer-common.cc b/src/snapshot/serializer-common.cc
index eeb7eb7..4afaa20 100644
--- a/src/snapshot/serializer-common.cc
+++ b/src/snapshot/serializer-common.cc
@@ -20,7 +20,10 @@
     Address addr = table->address(i);
     if (addr == ExternalReferenceTable::NotAvailable()) continue;
     // We expect no duplicate external references entries in the table.
-    DCHECK_NULL(map_->Lookup(addr, Hash(addr)));
+    // AccessorRefTable getter may have duplicates, indicated by an empty string
+    // as name.
+    DCHECK(table->name(i)[0] == '\0' ||
+           map_->Lookup(addr, Hash(addr)) == nullptr);
     map_->LookupOrInsert(addr, Hash(addr))->value = reinterpret_cast<void*>(i);
   }
   isolate->set_external_reference_map(map_);