Add Object::IsNullOrUndefined(Isolate*) helper method

src/full-codegen/x64/full-codegen-x64.cc

 // Copyright 2012 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ast/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/builtins/builtins-constructor.h"
 #include "src/code-factory.h"
@@ skipping 478 matching lines @@
     __ Push(lit);
   }
 }
 
 
 void FullCodeGenerator::TestContext::Plug(Handle<Object> lit) const {
   codegen()->PrepareForBailoutBeforeSplit(condition(),
                                           true,
                                           true_label_,
                                           false_label_);
-  DCHECK(lit->IsNull(isolate()) || lit->IsUndefined(isolate()) ||
-         !lit->IsUndetectable());
-  if (lit->IsUndefined(isolate()) || lit->IsNull(isolate()) ||
-      lit->IsFalse(isolate())) {
+  DCHECK(lit->IsNullOrUndefined(isolate()) || !lit->IsUndetectable());
+  if (lit->IsNullOrUndefined(isolate()) || lit->IsFalse(isolate())) {
     if (false_label_ != fall_through_) __ jmp(false_label_);
   } else if (lit->IsTrue(isolate()) || lit->IsJSObject()) {
     if (true_label_ != fall_through_) __ jmp(true_label_);
   } else if (lit->IsString()) {
     if (String::cast(*lit)->length() == 0) {
       if (false_label_ != fall_through_) __ jmp(false_label_);
     } else {
       if (true_label_ != fall_through_) __ jmp(true_label_);
     }
   } else if (lit->IsSmi()) {
@@ skipping 2174 matching lines @@
   DCHECK_EQ(
       isolate->builtins()->OnStackReplacement()->entry(),
       Assembler::target_address_at(call_target_address, unoptimized_code));
   return ON_STACK_REPLACEMENT;
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64