V8ObjectBuilder::addString support Nullable.

third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp

Index: third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp b/third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp
index 571f400aed419b717c9ef6fa39b60f33d737cb34..d797add21184c0d7ab36d96f38c459985b8cb149 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/V8ObjectBuilder.cpp
@@ -35,8 +35,13 @@ V8ObjectBuilder& V8ObjectBuilder::addNumber(const String& name, double value) {
 }
 
 V8ObjectBuilder& V8ObjectBuilder::addString(const String& name,
-                                            const String& value) {
-  addInternal(name, v8String(m_scriptState->isolate(), value));
+                                            const String& value,
+                                            bool isNullable) {
+  if (isNullable && value.isNull()) {
+    addInternal(name, v8::Null(m_scriptState->isolate()));
+  } else {
+    addInternal(name, v8String(m_scriptState->isolate(), value));
+  }
   return *this;
 }