Add pending preloads indexed by routing id. Start preloading once we navigate.

chrome/browser/prerender/prerender_final_status.h

 // Copyright (c) 2011 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 CHROME_BROWSER_PRERENDER_PRERENDER_FINAL_STATUS_H_
 #define CHROME_BROWSER_PRERENDER_PRERENDER_FINAL_STATUS_H_
 
 namespace prerender {
 
 // FinalStatus indicates whether |this| was used, or why it was cancelled.
 // NOTE: New values need to be appended, since they are used in histograms.
 enum FinalStatus {
   FINAL_STATUS_USED,
   FINAL_STATUS_TIMED_OUT,
   FINAL_STATUS_EVICTED,
   FINAL_STATUS_MANAGER_SHUTDOWN,
   FINAL_STATUS_CLOSED,
   FINAL_STATUS_CREATE_NEW_WINDOW,
   FINAL_STATUS_PROFILE_DESTROYED,
   FINAL_STATUS_APP_TERMINATING,
   FINAL_STATUS_JAVASCRIPT_ALERT,
   FINAL_STATUS_AUTH_NEEDED,
   FINAL_STATUS_HTTPS,
   FINAL_STATUS_DOWNLOAD,
   FINAL_STATUS_MEMORY_LIMIT_EXCEEDED,
   FINAL_STATUS_JS_OUT_OF_MEMORY,
   FINAL_STATUS_RENDERER_UNRESPONSIVE,
   FINAL_STATUS_TOO_MANY_PROCESSES,
   FINAL_STATUS_RATE_LIMIT_EXCEEDED,
-  FINAL_STATUS_NESTED,
+  FINAL_STATUS_PENDING_SKIPPED,
   FINAL_STATUS_MAX,
 };
 
 void RecordFinalStatus(FinalStatus final_status);
 
 }  // namespace prerender
 
 #endif  // CHROME_BROWSER_PRERENDER_PRERENDER_FINAL_STATUS_H_