Use sockets with unread data if they've never been used before.

net/socket/stream_socket.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_STREAM_SOCKET_H_
 #define NET_SOCKET_STREAM_SOCKET_H_
 
 #include "net/base/net_log.h"
 #include "net/socket/next_proto.h"
 #include "net/socket/socket.h"
@@ skipping 52 matching lines @@
 
   // Gets the NetLog for this socket.
   virtual const BoundNetLog& NetLog() const = 0;
 
   // Set the annotation to indicate this socket was created for speculative
   // reasons.  This call is generally forwarded to a basic TCPClientSocket*,
   // where a UseHistory can be updated.
   virtual void SetSubresourceSpeculation() = 0;
   virtual void SetOmniboxSpeculation() = 0;
 
-  // Returns true if the underlying transport socket ever had any reads or
-  // writes.  StreamSockets layered on top of transport sockets should forward
-  // this call to the transport socket.
+  // Returns true if the socket ever had any reads or writes.  StreamSockets
+  // layered on top of transport sockets should return if their own Read() or
+  // Write() methods had been called, not the underlying transport's.
   virtual bool WasEverUsed() const = 0;
 
   // Returns true if the underlying transport socket is using TCP FastOpen.
   // TCP FastOpen is an experiment with sending data in the TCP SYN packet.
   virtual bool UsingTCPFastOpen() const = 0;
 
   // Returns true if NPN was negotiated during the connection of this socket.
   virtual bool WasNpnNegotiated() const = 0;
 
   // Returns the protocol negotiated via NPN for this socket, or
@@ skipping 43 matching lines @@
     // identify the motivation.
     bool omnibox_speculation_;
     bool subresource_speculation_;
     DISALLOW_COPY_AND_ASSIGN(UseHistory);
   };
 };
 
 }  // namespace net
 
 #endif  // NET_SOCKET_STREAM_SOCKET_H_