Reland my close on idle socket change.

net/socket/client_socket_pool_base.h

 // Copyright (c) 2010 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.
 //
 // A ClientSocketPoolBase is used to restrict the number of sockets open at
 // a time.  It also maintains a list of idle persistent sockets for reuse.
 // Subclasses of ClientSocketPool should compose ClientSocketPoolBase to handle
 // the core logic of (1) restricting the number of active (connected or
 // connecting) sockets per "group" (generally speaking, the hostname), (2)
 // maintaining a per-group list of idle, persistent sockets for reuse, and (3)
@@ skipping 207 matching lines @@
   }
 
   // Closes all idle sockets if |force| is true.  Else, only closes idle
   // sockets that timed out or can't be reused.  Made public for testing.
   void CleanupIdleSockets(bool force);
 
   base::TimeDelta ConnectionTimeout() const {
     return connect_job_factory_->ConnectionTimeout();
   }
 
-  void enable_backup_jobs() { backup_jobs_enabled_ = true; };
+  void EnableBackupJobs() { backup_jobs_enabled_ = true; };
 
  private:
   friend class base::RefCounted<ClientSocketPoolBaseHelper>;
 
   ~ClientSocketPoolBaseHelper();
 
   // Entry for a persistent socket which became idle at time |start_time|.
   struct IdleSocket {
     IdleSocket() : socket(NULL), used(false) {}
     ClientSocket* socket;
@@ skipping 141 matching lines @@
   // |request|.
   int RequestSocketInternal(const std::string& group_name,
                             const Request* request);
 
   // Set a timer to create a backup socket if it takes too long to create one.
   void StartBackupSocketTimer(const std::string& group_name);
 
   // Called when the backup socket timer fires.
   void OnBackupSocketTimerFired(const std::string& group_name);
 
+  // Closes one idle socket.  Picks the first one encountered.
+  // TODO(willchan): Consider a better algorithm for doing this.  Perhaps we
+  // should keep an ordered list of idle sockets, and close them in order.
+  // Requires maintaining more state.  It's not clear if it's worth it since
+  // I'm not sure if we hit this situation often.
+  void CloseOneIdleSocket();
+
   GroupMap group_map_;
 
   // Timer used to periodically prune idle sockets that timed out or can't be
   // reused.
   base::RepeatingTimer<ClientSocketPoolBaseHelper> timer_;
 
   // The total number of idle sockets in the system.
   int idle_socket_count_;
 
   // Number of connecting sockets across all groups.
@@ skipping 19 matching lines @@
   // have pending requests if it exceeds the "max sockets per group" limit.
   //
   // This means when a socket is released, the only pending requests that can
   // be started next belong to the same group.
   //
   // However once the |max_sockets_| limit is reached, this stops being true:
   // groups can now have pending requests without having first reached the
   // |max_sockets_per_group_| limit. So choosing the next request involves
   // selecting the highest priority request across *all* groups.
   //
-  // Since reaching the maximum number of sockets is an edge case, we make note
-  // of when it happens, and thus avoid doing the slower "scan all groups"
-  // in the common case.
+  // |may_have_stalled_group_| is not conclusive, since when we cancel pending
+  // requests, we may reach the situation where we have the maximum number of 
+  // sockets, but not request is stalled because of the global socket limit
+  // (although some requests may be blocked on the socket per group limit).
+  // We don't strictly maintain |may_have_stalled_group_|, since that would
+  // require a linear search through all groups in |group_map_| to see if one 
+  // of them is stalled.
   bool may_have_stalled_group_;
 
   const scoped_ptr<ConnectJobFactory> connect_job_factory_;
 
   // TODO(vandebo) Remove when backup jobs move to TCPClientSocketPool
   bool backup_jobs_enabled_;
 
   // A factory to pin the backup_job tasks.
   ScopedRunnableMethodFactory<ClientSocketPoolBaseHelper> method_factory_;
 };
@@ skipping 119 matching lines @@
   void CleanupIdleSockets(bool force) {
     return helper_->CleanupIdleSockets(force);
   }
 
   base::TimeDelta ConnectionTimeout() const {
     return helper_->ConnectionTimeout();
   }
 
   const std::string& name() const { return name_; }
 
-  void enable_backup_jobs() { helper_->enable_backup_jobs(); };
+  void EnableBackupJobs() { helper_->EnableBackupJobs(); };
 
  private:
   // This adaptor class exists to bridge the
   // internal::ClientSocketPoolBaseHelper::ConnectJobFactory and
   // ClientSocketPoolBase::ConnectJobFactory types, allowing clients to use the
   // typesafe ClientSocketPoolBase::ConnectJobFactory, rather than having to
   // static_cast themselves.
   class ConnectJobFactoryAdaptor
       : public internal::ClientSocketPoolBaseHelper::ConnectJobFactory {
    public:
@@ skipping 31 matching lines @@
   // the posting of the task and the execution, then we'll hit the DCHECK that
   // |ClientSocketPoolBaseHelper::group_map_| is empty.
   scoped_refptr<internal::ClientSocketPoolBaseHelper> helper_;
 
   DISALLOW_COPY_AND_ASSIGN(ClientSocketPoolBase);
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_CLIENT_SOCKET_POOL_BASE_H_