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

third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp

Index: third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp
diff --git a/third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp b/third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp
index cab6504fb71717a72333aa997bc678375e5388e8..4a1ca73ada2e454cb4cae7e29017d428f03a42e2 100644
--- a/third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp
+++ b/third_party/WebKit/Source/modules/webmidi/MIDIPort.cpp
@@ -69,7 +69,7 @@ String MIDIPort::connection() const {
     case ConnectionStatePending:
       return "pending";
   }
-  return emptyString();
+  return emptyString;
 }
 
 String MIDIPort::state() const {
@@ -82,7 +82,7 @@ String MIDIPort::state() const {
       NOTREACHED();
       return "connected";
   }
-  return emptyString();
+  return emptyString;
 }
 
 String MIDIPort::type() const {
@@ -92,7 +92,7 @@ String MIDIPort::type() const {
     case TypeOutput:
       return "output";
   }
-  return emptyString();
+  return emptyString;
 }
 
 ScriptPromise MIDIPort::open(ScriptState* scriptState) {