Add Prerender type to NavigationType for nav timing 2

third_party/WebKit/Source/core/timing/PerformanceNavigation.h

 /*
  * Copyright (C) 2010 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 24 matching lines @@
 #include "core/CoreExport.h"
 #include "core/frame/DOMWindowProperty.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class LocalFrame;
 class ScriptState;
 class ScriptValue;
 
+// Legacy support for NT1(https://www.w3.org/TR/navigation-timing/).
 class CORE_EXPORT PerformanceNavigation final
     : public GarbageCollected<PerformanceNavigation>,
       public ScriptWrappable,
       public DOMWindowProperty {
   DEFINE_WRAPPERTYPEINFO();
   USING_GARBAGE_COLLECTED_MIXIN(PerformanceNavigation);
 
  public:
   static PerformanceNavigation* create(LocalFrame* frame) {
     return new PerformanceNavigation(frame);
@@ skipping 13 matching lines @@
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
   explicit PerformanceNavigation(LocalFrame*);
 };
 
 }  // namespace blink
 
 #endif  // PerformanceNavigation_h