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

third_party/WebKit/Source/core/dom/Document.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved.
  * (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
@@ skipping 970 matching lines @@
 
   void updateFocusAppearanceLater();
   void cancelFocusAppearanceUpdate();
 
   bool isDNSPrefetchEnabled() const { return m_isDNSPrefetchEnabled; }
   void parseDNSPrefetchControlHeader(const String&);
 
   void postTask(TaskType,
                 const WebTraceLocation&,
                 std::unique_ptr<ExecutionContextTask>,
-                const String& taskNameForInstrumentation = emptyString())
+                const String& taskNameForInstrumentation = emptyString)
       override;  // Executes the task on context's thread asynchronously.
 
   void tasksWereSuspended() final;
   void tasksWereResumed() final;
   bool tasksNeedSuspension() final;
 
   void finishedParsing();
 
   void setEncodingData(const DocumentEncodingData& newData);
   const WTF::TextEncoding& encoding() const {
@@ skipping 719 matching lines @@
 DEFINE_TYPE_CASTS(TreeScope, Document, document, true, true);
 
 }  // namespace blink
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 CORE_EXPORT void showLiveDocumentInstances();
 #endif
 
 #endif  // Document_h