Use a new Supplement constructor for supplements in core/

third_party/WebKit/Source/core/loader/PrerendererClient.cpp

 /*
  * 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:
  *
  *     * 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 26 matching lines @@
 
 // static
 const char* PrerendererClient::supplementName() {
   return "PrerendererClient";
 }
 
 // static
 PrerendererClient* PrerendererClient::from(Page* page) {
   PrerendererClient* supplement = static_cast<PrerendererClient*>(
       Supplement<Page>::from(page, supplementName()));
+  DCHECK(supplement);
   return supplement;
 }
 
+PrerendererClient::PrerendererClient(Page& page) : Supplement<Page>(page) {}
+
 void providePrerendererClientTo(Page& page, PrerendererClient* client) {
   PrerendererClient::provideTo(page, PrerendererClient::supplementName(),
                                client);
 }
 
 }  // namespace blink