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

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

 /*
  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
  * 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
@@ skipping 86 matching lines @@
   const KURL& url() const;
   KURL completeURL(const String& url) const;
   virtual void disableEval(const String& errorMessage) = 0;
   virtual LocalDOMWindow* executingWindow() const { return 0; }
   virtual String userAgent() const = 0;
   // Executes the task on context's thread asynchronously.
   virtual void postTask(
       TaskType,
       const WebTraceLocation&,
       std::unique_ptr<ExecutionContextTask>,
-      const String& taskNameForInstrumentation = emptyString()) = 0;
+      const String& taskNameForInstrumentation = emptyString) = 0;
 
   // Gets the DOMTimerCoordinator which maintains the "active timer
   // list" of tasks created by setTimeout and setInterval. The
   // DOMTimerCoordinator is owned by the ExecutionContext and should
   // not be used after the ExecutionContext is destroyed.
   virtual DOMTimerCoordinator* timers() = 0;
 
   virtual SecurityContext& securityContext() = 0;
   KURL contextURL() const { return virtualURL(); }
   KURL contextCompleteURL(const String& url) const {
@@ skipping 96 matching lines @@
   // |allowWindowInteraction()| and |consumeWindowInteraction()| in order to
   // increment and decrement the counter.
   int m_windowInteractionTokens;
 
   ReferrerPolicy m_referrerPolicy;
 };
 
 }  // namespace blink
 
 #endif  // ExecutionContext_h