Ensure slow properties for simple {__proto__:null} literals.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index f67e7b927c28e4a9502c50b1ae98b1c652d48cf9..be7b13c8d8e5c5c0ea72209cc381be3364285302 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1743,6 +1743,7 @@ void BytecodeGenerator::VisitObjectLiteral(ObjectLiteral* expr) {
         break;
       }
       case ObjectLiteral::Property::PROTOTYPE: {
+        if (property->IsNullPrototype()) break;
         DCHECK(property->emit_store());
         RegisterList args = register_allocator()->NewRegisterList(2);
         builder()->MoveRegister(literal, args[0]);
@@ -1792,7 +1793,9 @@ void BytecodeGenerator::VisitObjectLiteral(ObjectLiteral* expr) {
     ObjectLiteral::Property* property = expr->properties()->at(property_index);
     RegisterAllocationScope inner_register_scope(this);
 
-    if (property->kind() == ObjectLiteral::Property::PROTOTYPE) {
+    if (property->IsPrototype()) {
+      // __proto__:null is handled by CreateObjectLiteral.
+      if (property->IsNullPrototype()) continue;
       DCHECK(property->emit_store());
       RegisterList args = register_allocator()->NewRegisterList(2);
       builder()->MoveRegister(literal, args[0]);