Add map-based read barrier to WeakCell

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 8226a0e5d7f0e92dfe4775a327fee2776b16a55e..b07a184c5c856615bc80ad69b3d6b20b411018aa 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -2444,7 +2444,7 @@ Handle<Map> Factory::ObjectLiteralMapFromCache(Handle<Context> context,
     if (result->IsWeakCell()) {
       WeakCell* cell = WeakCell::cast(result);
       if (!cell->cleared()) {
-        return handle(Map::cast(cell->value()), isolate());
+        return handle(Map::cast(cell->value(isolate()->heap())), isolate());
       }
     }
   }