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

third_party/WebKit/Source/platform/mojo/KURLStructTraits.h

 // Copyright 2016 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 KURLStructTraits_h
 #define KURLStructTraits_h
 
 #include "platform/weborigin/KURL.h"
 #include "url/mojo/url.mojom-blink.h"
 #include "url/url_constants.h"
 #include "wtf/text/WTFString.h"
 
 namespace mojo {
 
 template <>
 struct StructTraits<url::mojom::blink::Url::DataView, ::blink::KURL> {
   static WTF::String url(const ::blink::KURL& blinkUrl) {
     if (!blinkUrl.isValid() ||
         blinkUrl.getString().length() > url::kMaxURLChars) {
-      return emptyString();
+      return emptyString;
     }
 
     return blinkUrl.getString();
   }
   static bool Read(url::mojom::blink::Url::DataView data, ::blink::KURL* out) {
     WTF::String urlString;
     if (!data.ReadUrl(&urlString))
       return false;
 
     if (urlString.length() > url::kMaxURLChars)
       return false;
 
     *out = ::blink::KURL(::blink::KURL(), urlString);
     if (!urlString.isEmpty() && !out->isValid())
       return false;
 
     return true;
   }
 };
 }
 
 #endif  // KURLStructTraits_h