Prioritize which HTTP requests get a socket first by adding a priority level ...

net/base/client_socket_pool.h

Index: net/base/client_socket_pool.h
===================================================================
--- net/base/client_socket_pool.h	(revision 12453)
+++ net/base/client_socket_pool.h	(working copy)
@@ -35,7 +35,8 @@
   // handle will be initialized without a socket such that the consumer needs
   // to supply a socket, or 3) the handle will be added to a wait list until a
   // socket is available to reuse or the opportunity to create a new socket
-  // arises.  The completion callback is notified in the 3rd case.
+  // arises.  The completion callback is notified in the 3rd case.  |priority|
+  // will determine the placement into the wait list.
   //
   // If this function returns OK, then |handle| is initialized upon return.
   // The |handle|'s is_initialized method will return true in this case.  If a
@@ -47,7 +48,9 @@
   // If ERR_IO_PENDING is returned, then the completion callback will be called
   // when |handle| has been initialized.
   //
-  int RequestSocket(ClientSocketHandle* handle, CompletionCallback* callback);
+  int RequestSocket(ClientSocketHandle* handle,
+                    int priority,
+                    CompletionCallback* callback);
 
   // Called to cancel a RequestSocket call that returned ERR_IO_PENDING.  The
   // same handle parameter must be passed to this method as was passed to the
@@ -75,30 +78,12 @@
 
   typedef scoped_ptr<ClientSocket> ClientSocketPtr;
 
-  ~ClientSocketPool();
-
-  // Closes all idle sockets if |force| is true.  Else, only closes idle
-  // sockets that timed out or can't be reused.
-  void CleanupIdleSockets(bool force);
-
-  // Called when the number of idle sockets changes.
-  void IncrementIdleCount();
-  void DecrementIdleCount();
-
-  // Called via PostTask by ReleaseSocket.
-  void DoReleaseSocket(const std::string& group_name, ClientSocketPtr* ptr);
-
-  // Called when timer_ fires.  This method scans the idle sockets removing
-  // sockets that timed out or can't be reused.
-  void OnCleanupTimerFired() {
-    CleanupIdleSockets(false);
-  }
-
   // A Request is allocated per call to RequestSocket that results in
   // ERR_IO_PENDING.
   struct Request {
     ClientSocketHandle* handle;
     CompletionCallback* callback;
+    int priority;
   };
 
   // Entry for a persistent socket which became idle at time |start_time|.
@@ -116,16 +101,41 @@
     bool ShouldCleanup(base::TimeTicks now) const;
   };
 
+  typedef std::deque<Request> RequestQueue;
+
   // A Group is allocated per group_name when there are idle sockets or pending
   // requests.  Otherwise, the Group object is removed from the map.
   struct Group {
     Group() : active_socket_count(0) {}
     std::deque<IdleSocket> idle_sockets;
-    std::deque<Request> pending_requests;
+    RequestQueue pending_requests;
     int active_socket_count;
   };
 
   typedef std::map<std::string, Group> GroupMap;
+
+  ~ClientSocketPool();
+
+  static void InsertRequestIntoQueue(const Request& r,
+                                     RequestQueue* pending_requests);
+
+  // Closes all idle sockets if |force| is true.  Else, only closes idle
+  // sockets that timed out or can't be reused.
+  void CleanupIdleSockets(bool force);
+
+  // Called when the number of idle sockets changes.
+  void IncrementIdleCount();
+  void DecrementIdleCount();
+
+  // Called via PostTask by ReleaseSocket.
+  void DoReleaseSocket(const std::string& group_name, ClientSocketPtr* ptr);
+
+  // Called when timer_ fires.  This method scans the idle sockets removing
+  // sockets that timed out or can't be reused.
+  void OnCleanupTimerFired() {
+    CleanupIdleSockets(false);
+  }
+
   GroupMap group_map_;
 
   // Timer used to periodically prune idle sockets that timed out or can't be