Avoid doing concurrent DNS resolves of the same hostname

chrome/browser/net/dns_global.cc

 // 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.
 
 #include "chrome/browser/net/dns_global.h"
 
 #include <map>
 #include <string>
 
 #include "base/singleton.h"
@@ skipping 411 matching lines @@
 }
 
 //------------------------------------------------------------------------------
 
 // Host resolver shared by DNS prefetcher, and the main URLRequestContext.
 static net::HostResolver* global_host_resolver = NULL;
 
 net::HostResolver* GetGlobalHostResolver() {
   // Called from UI thread.
   if (!global_host_resolver) {
-  // TODO(eroman):
-#if 0
     static const size_t kMaxHostCacheEntries = 100;
     static const size_t kHostCacheExpirationSeconds = 60;  // 1 minute.
 
     global_host_resolver = new net::HostResolver(
         kMaxHostCacheEntries, kHostCacheExpirationSeconds * 1000);
-#endif
   }
   return global_host_resolver;
 }
 
 void FreeGlobalHostResolver() {
   if (global_host_resolver) {
     // Called from IO thread.
-    DCHECK_EQ(MessageLoop::current(),
-              g_browser_process->io_thread()->message_loop());
     delete global_host_resolver;
     global_host_resolver = NULL;
   }
 }
 
 //------------------------------------------------------------------------------
 // Functions to handle saving of hostnames from one session to the next, to
 // expedite startup times.
 
 void SaveHostNamesForNextStartup(PrefService* local_state) {
@@ skipping 61 matching lines @@
   dns_master->DeserializeReferrers(*referral_list);
 }
 
 void TrimSubresourceReferrers() {
   if (NULL == dns_master)
     return;
   dns_master->TrimReferrers();
 }
 
 }  // namespace chrome_browser_net