Avoid doing concurrent DNS resolves of the same hostname

net/http/http_cache.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 file declares a HttpTransactionFactory implementation that can be
 // layered on top of another HttpTransactionFactory to add HTTP caching.  The
 // caching logic follows RFC 2616 (any exceptions are called out in the code).
 //
 // The HttpCache takes a disk_cache::Backend as a parameter, and uses that for
 // the cache storage.
@@ skipping 13 matching lines @@
 #include "net/base/cache_type.h"
 #include "net/http/http_transaction_factory.h"
 
 namespace disk_cache {
 class Backend;
 class Entry;
 }
 
 namespace net {
 
+class HostResolver;
 class HttpNetworkSession;
 class HttpRequestInfo;
 class HttpResponseInfo;
 class ProxyService;
 
 class HttpCache : public HttpTransactionFactory {
  public:
   ~HttpCache();
 
   // The cache mode of operation.
   enum Mode {
     // Normal mode just behaves like a standard web cache.
     NORMAL = 0,
     // Record mode caches everything for purposes of offline playback.
     RECORD,
     // Playback mode replays from a cache without considering any
     // standard invalidations.
     PLAYBACK,
     // Disables reads and writes from the cache.
     // Equivalent to setting LOAD_DISABLE_CACHE on every request.
     DISABLE
   };
 
   // Initialize the cache from the directory where its data is stored. The
   // disk cache is initialized lazily (by CreateTransaction) in this case. If
   // |cache_size| is zero, a default value will be calculated automatically.
-  HttpCache(ProxyService* proxy_service,
+  HttpCache(HostResolver* host_resolver,
+            ProxyService* proxy_service,
             const std::wstring& cache_dir,
             int cache_size);
 
   // Initialize the cache from the directory where its data is stored. The
   // disk cache is initialized lazily (by CreateTransaction) in  this case. If
   // |cache_size| is zero, a default value will be calculated automatically.
   // Provide an existing HttpNetworkSession, the cache can construct a
   // network layer with a shared HttpNetworkSession in order for multiple
   // network layers to share information (e.g. authenication data).
   HttpCache(HttpNetworkSession* session, const std::wstring& cache_dir,
             int cache_size);
 
   // Initialize using an in-memory cache. The cache is initialized lazily
   // (by CreateTransaction) in this case. If |cache_size| is zero, a default
   // value will be calculated automatically.
-  HttpCache(ProxyService* proxy_service, int cache_size);
+  HttpCache(HostResolver* host_resolver,
+            ProxyService* proxy_service,
+            int cache_size);
 
   // Initialize the cache from its component parts, which is useful for
   // testing.  The lifetime of the network_layer and disk_cache are managed by
   // the HttpCache and will be destroyed using |delete| when the HttpCache is
   // destroyed.
   HttpCache(HttpTransactionFactory* network_layer,
             disk_cache::Backend* disk_cache);
 
   HttpTransactionFactory* network_layer() { return network_layer_.get(); }
   disk_cache::Backend* disk_cache() { return disk_cache_.get(); }
@@ skipping 98 matching lines @@
   scoped_ptr<PlaybackCacheMap> playback_cache_map_;
 
   RevocableStore transactions_;
 
   DISALLOW_COPY_AND_ASSIGN(HttpCache);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_H_