Replace WTF::emptyString{16Bit}() with a static global

third_party/WebKit/Source/core/html/shadow/DateTimeEditElement.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
@@ skipping 828 matching lines @@
 
 void DateTimeEditElement::updateUIState() {
   if (isDisabled()) {
     if (DateTimeFieldElement* field = focusedField())
       field->blur();
   }
 }
 
 String DateTimeEditElement::value() const {
   if (!m_editControlOwner)
-    return emptyString();
+    return emptyString;
   return m_editControlOwner->formatDateTimeFieldsState(
       valueAsDateTimeFieldsState());
 }
 
 DateTimeFieldsState DateTimeEditElement::valueAsDateTimeFieldsState() const {
   DateTimeFieldsState dateTimeFieldsState;
   for (const auto& field : m_fields)
     field->populateDateTimeFieldsState(dateTimeFieldsState);
   return dateTimeFieldsState;
 }
 
 }  // namespace blink