Add Object::IsNullOrUndefined(Isolate*) helper method

src/ic/handler-compiler.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/ic/handler-compiler.h"
 
 #include "src/field-type.h"
 #include "src/ic/call-optimization.h"
 #include "src/ic/handler-configuration-inl.h"
 #include "src/ic/ic-inl.h"
@@ skipping 143 matching lines @@
                                                         Label* miss,
                                                         Register scratch1,
                                                         Register scratch2) {
   Register holder_reg;
   Handle<Map> last_map;
   if (holder().is_null()) {
     holder_reg = receiver();
     last_map = map();
     // If |type| has null as its prototype, |holder()| is
     // Handle<JSObject>::null().
-    DCHECK(last_map->prototype() == isolate()->heap()->null_value());
+    DCHECK(last_map->prototype()->IsNull(isolate()));
   } else {
     last_map = handle(holder()->map());
     // This condition matches the branches below.
     bool need_holder =
         last_map->is_dictionary_map() && !last_map->IsJSGlobalObjectMap();
     holder_reg =
         FrontendHeader(receiver(), name, miss,
                        need_holder ? RETURN_HOLDER : DONT_RETURN_ANYTHING);
   }
 
@@ skipping 323 matching lines @@
 }
 
 void ElementHandlerCompiler::CompileElementHandlers(
     MapHandleList* receiver_maps, List<Handle<Object>>* handlers) {
   for (int i = 0; i < receiver_maps->length(); ++i) {
     handlers->Add(GetKeyedLoadHandler(receiver_maps->at(i), isolate()));
   }
 }
 }  // namespace internal
 }  // namespace v8