Clean up dns prefetch code, and also port it.

chrome/browser/net/dns_global.h

 // Copyright (c) 2006-2008 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.
 
 // This is the global interface for the dns prefetch services.  It centralizes
 // initialization, along with all the callbacks etc. to connect to the browser
 // process.  This allows the more standard DNS prefetching services, such as
 // provided by DnsMaster to be left as more generally usable code, and possibly
 // be shared across multiple client projects.
 
 #ifndef CHROME_BROWSER_NET_DNS_GLOBAL_H_
 #define CHROME_BROWSER_NET_DNS_GLOBAL_H_
 
 #include "chrome/browser/net/dns_master.h"
 
 #include <string>
 
 class PrefService;
 
 namespace chrome_browser_net {
 
-// Functions to initialize our global state so that PrefetchDns() can be called.
+// Initialize dns prefetching subsystem. Must be called before any other
+// functions.
 void InitDnsPrefetch(PrefService* user_prefs);
+
+// Cancel pending lookup requests and don't make new ones.
 void ShutdownDnsPrefetch();
 
+// Free all resources allocated by InitDnsPrefetch. After that you must not call
+// any function from this file.
+void FreeDnsPrefetchResources();
+
 //------------------------------------------------------------------------------
 // Global APIs relating to Prefetching in browser
 void EnableDnsPrefetch(bool enable);
 void RegisterPrefs(PrefService* local_state);
 void RegisterUserPrefs(PrefService* user_prefs);
 // Renderer bundles up list and sends to this browser API via IPC.
 void DnsPrefetchList(const NameList& hostnames);
 // This API is used by the autocomplete popup box (as user types).
 void DnsPrefetchUrl(const GURL& url);
 void DnsPrefetchGetHtmlInfo(std::string* output);
@@ skipping 10 matching lines @@
 void RestoreSubresourceReferrers(PrefService* local_state);
 void TrimSubresourceReferrers();
 
 //------------------------------------------------------------------------------
 // Helper class to handle global init and shutdown.
 class DnsPrefetcherInit {
  public:
   explicit DnsPrefetcherInit(PrefService* user_prefs) {
     InitDnsPrefetch(user_prefs);
   }
-  ~DnsPrefetcherInit() {ShutdownDnsPrefetch();}
+
+  ~DnsPrefetcherInit() {
+    FreeDnsPrefetchResources();
+  }
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DnsPrefetcherInit);
 };
 
 }  // namespace chrome_browser_net
 
 #endif  // CHROME_BROWSER_NET_DNS_GLOBAL_H_