Revert 129277 - Revert 127893 - Attempting to re-land the feature.

net/socket/client_socket_pool.h

Index: net/socket/client_socket_pool.h
===================================================================
--- net/socket/client_socket_pool.h	(revision 129292)
+++ net/socket/client_socket_pool.h	(working copy)
@@ -29,6 +29,17 @@
 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.
 //
@@ -110,6 +121,10 @@
   // 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;
 
@@ -123,6 +138,12 @@
   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