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

third_party/WebKit/Source/core/testing/NullExecutionContext.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NullExecutionContext_h
 #define NullExecutionContext_h
 
 #include "bindings/core/v8/SourceLocation.h"
 #include "core/dom/ExecutionContext.h"
 #include "core/dom/SecurityContext.h"
@@ skipping 14 matching lines @@
  public:
   NullExecutionContext();
 
   void disableEval(const String&) override {}
   String userAgent() const override { return String(); }
 
   void postTask(
       TaskType,
       const WebTraceLocation&,
       std::unique_ptr<ExecutionContextTask>,
-      const String& taskNameForInstrumentation = emptyString()) override;
+      const String& taskNameForInstrumentation = emptyString) override;
 
   EventTarget* errorEventTarget() override { return nullptr; }
   EventQueue* getEventQueue() const override { return m_queue.get(); }
 
   bool tasksNeedSuspension() override { return m_tasksNeedSuspension; }
   void setTasksNeedSuspension(bool flag) { m_tasksNeedSuspension = flag; }
 
   void didUpdateSecurityOrigin() override {}
   SecurityContext& securityContext() override { return *this; }
   DOMTimerCoordinator* timers() override { return nullptr; }
@@ skipping 20 matching lines @@
   bool m_tasksNeedSuspension;
   bool m_isSecureContext;
   Member<EventQueue> m_queue;
 
   KURL m_dummyURL;
 };
 
 }  // namespace blink
 
 #endif  // NullExecutionContext_h