base: Add three helper functions to Values API.

chrome/browser/automation/automation_provider_observers.cc

Index: chrome/browser/automation/automation_provider_observers.cc
diff --git a/chrome/browser/automation/automation_provider_observers.cc b/chrome/browser/automation/automation_provider_observers.cc
index 3f2a306867b7f394242b6542a1415119f44c4316..f2e394a450141029e2a3ba8e8a3db97a2352c755 100644
--- a/chrome/browser/automation/automation_provider_observers.cc
+++ b/chrome/browser/automation/automation_provider_observers.cc
@@ -141,7 +141,7 @@ DictionaryValue* InitialLoadObserver::GetTimingInformation() const {
 
     item->SetDouble("load_start_ms", delta_start.InMillisecondsF());
     if (it->second.stop_time().is_null()) {
-      item->Set("load_stop_ms", Value::CreateNullValue());
+      item->Set("load_stop_ms", base::NullValue());
     } else {
       base::TimeDelta delta_stop = it->second.stop_time() - init_time_;
       item->SetDouble("load_stop_ms", delta_stop.InMillisecondsF());