Attempting to re-land a small portion of this change... Simply add links from

net/socket/client_socket_pool.h

 // Copyright (c) 2012 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 NET_SOCKET_CLIENT_SOCKET_POOL_H_
 #define NET_SOCKET_CLIENT_SOCKET_POOL_H_
 #pragma once
 
 #include <deque>
 #include <string>
@@ skipping 11 matching lines @@
 namespace base {
 class DictionaryValue;
 }
 
 namespace net {
 
 class ClientSocketHandle;
 class ClientSocketPoolHistograms;
 class StreamSocket;
 
+// ClientSocketPools are layered. This defines an interface for lower level
+// socket pools to communicate with higher layer pools.
+class NET_EXPORT LayeredPool {
+ public:
+  virtual ~LayeredPool() {};
+
+  // Instructs the LayeredPool to close an idle connection. Return true if one
+  // was closed.
+  virtual bool CloseOneIdleConnection() = 0;
+};
+
 // A ClientSocketPool is used to restrict the number of sockets open at a time.
 // It also maintains a list of idle persistent sockets.
 //
 class NET_EXPORT ClientSocketPool {
  public:
   // Requests a connected socket for a group_name.
   //
   // There are five possible results from calling this function:
   // 1) RequestSocket returns OK and initializes |handle| with a reused socket.
   // 2) RequestSocket returns OK with a newly connected socket.
@@ skipping 61 matching lines @@
   virtual void ReleaseSocket(const std::string& group_name,
                              StreamSocket* socket,
                              int id) = 0;
 
   // This flushes all state from the ClientSocketPool.  This means that all
   // idle and connecting sockets are discarded.  Active sockets being
   // held by ClientSocketPool clients will be discarded when released back to
   // the pool.  Does not flush any pools wrapped by |this|.
   virtual void Flush() = 0;
 
+  // Returns true if a there is currently a request blocked on the
+  // per-pool (not per-host) max socket limit.
+  virtual bool IsStalled() const = 0;
+
   // Called to close any idle connections held by the connection manager.
   virtual void CloseIdleSockets() = 0;
 
   // The total number of idle sockets in the pool.
   virtual int IdleSocketCount() const = 0;
 
   // The total number of idle sockets in a connection group.
   virtual int IdleSocketCountInGroup(const std::string& group_name) const = 0;
 
   // Determine the LoadState of a connecting ClientSocketHandle.
   virtual LoadState GetLoadState(const std::string& group_name,
                                  const ClientSocketHandle* handle) const = 0;
 
+  // Adds a LayeredPool on top of |this|.
+  virtual void AddLayeredPool(LayeredPool* layered_pool) = 0;
+
+  // Removes a LayeredPool from |this|.
+  virtual void RemoveLayeredPool(LayeredPool* layered_pool) = 0;
+
   // Retrieves information on the current state of the pool as a
   // DictionaryValue.  Caller takes possession of the returned value.
   // If |include_nested_pools| is true, the states of any nested
   // ClientSocketPools will be included.
   virtual base::DictionaryValue* GetInfoAsValue(
       const std::string& name,
       const std::string& type,
       bool include_nested_pools) const = 0;
 
   // Returns the maximum amount of time to wait before retrying a connect.
@@ skipping 54 matching lines @@
                            const scoped_refptr<SocketParams>& params,
                            int num_sockets,
                            const BoundNetLog& net_log) {
   CheckIsValidSocketParamsForPool<PoolType, SocketParams>();
   pool->RequestSockets(group_name, &params, num_sockets, net_log);
 }
 
 }  // namespace net
 
 #endif  // NET_SOCKET_CLIENT_SOCKET_POOL_H_