V8ObjectBuilder::addString support Nullable.

third_party/WebKit/Source/bindings/bindings.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # All paths in this file should be absolute so it can be imported into
 # different contexts.
 
 import("//third_party/WebKit/Source/bindings/modules/v8/v8.gni")
 
 bindings_core_v8_files =
@@ skipping 219 matching lines @@
                     "core/v8/ScriptPromiseTest.cpp",
                     "core/v8/ScriptStreamerTest.cpp",
                     "core/v8/ScriptValueSerializerTest.cpp",
                     "core/v8/ScriptWrappableVisitorTest.cpp",
                     "core/v8/SerializedScriptValueTest.cpp",
                     "core/v8/ToV8Test.cpp",
                     "core/v8/TraceWrapperMemberTest.cpp",
                     "core/v8/V8BindingForTesting.cpp",
                     "core/v8/V8BindingForTesting.h",
                     "core/v8/V8BindingTest.cpp",
+                    "core/v8/V8ObjectBuilderTest.cpp",
                     "core/v8/V8ScriptRunnerTest.cpp",
                     "core/v8/serialization/V8ScriptValueSerializerTest.cpp",
                   ],
                   "abspath")
 bindings_unittest_files += bindings_modules_v8_unittest_files