net: merge two versions of SetTCPNoDelay() function into one

net/socket/tcp_socket.h

Index: net/socket/tcp_socket.h
diff --git a/net/socket/tcp_socket.h b/net/socket/tcp_socket.h
index 58797bb0851ca59cab11cd6ab7aa6c0d5c90dbaf..319a6b261d02f78961b3d950648f230dd0733857 100644
--- a/net/socket/tcp_socket.h
+++ b/net/socket/tcp_socket.h
@@ -7,6 +7,7 @@
 
 #include "build/build_config.h"
 #include "net/base/net_export.h"
+#include "net/socket/socket_descriptor.h"
 
 #if defined(OS_WIN)
 #include "net/socket/tcp_socket_win.h"
@@ -39,6 +40,39 @@ bool IsTCPFastOpenUserEnabled();
 // Not thread safe.  Must be called during initialization/startup only.
 NET_EXPORT void CheckSupportAndMaybeEnableTCPFastOpen(bool user_enabled);
 
+// This function enables/disables buffering in the kernel. By default, on Linux,
+// TCP sockets will wait up to 200ms for more data to complete a packet before
+// transmitting. After calling this function, the kernel will not wait. See
+// TCP_NODELAY in `man 7 tcp`.
+//
+// For Windows:
+//
+// The Nagle implementation on Windows is governed by RFC 896.  The idea
+// behind Nagle is to reduce small packets on the network.  When Nagle is
+// enabled, if a partial packet has been sent, the TCP stack will disallow
+// further *partial* packets until an ACK has been received from the other
+// side.  Good applications should always strive to send as much data as
+// possible and avoid partial-packet sends.  However, in most real world
+// applications, there are edge cases where this does not happen, and two
+// partial packets may be sent back to back.  For a browser, it is NEVER
+// a benefit to delay for an RTT before the second packet is sent.
+//
+// As a practical example in Chromium today, consider the case of a small
+// POST.  I have verified this:
+//     Client writes 649 bytes of header  (partial packet #1)
+//     Client writes 50 bytes of POST data (partial packet #2)
+// In the above example, with Nagle, a RTT delay is inserted between these
+// two sends due to nagle.  RTTs can easily be 100ms or more.  The best
+// fix is to make sure that for POSTing data, we write as much data as
+// possible and minimize partial packets.  We will fix that.  But disabling
+// Nagle also ensure we don't run into this delay in other edge cases.
+// See also:
+//    http://technet.microsoft.com/en-us/library/bb726981.aspx
+//
+// This function returns true if it succeeds to set the TCP_NODELAY option,
+// otherwise returns false.
+NET_EXPORT_PRIVATE bool SetTCPNoDelay(SocketDescriptor socket, bool no_delay);
+
 }  // namespace net
 
 #endif  // NET_SOCKET_TCP_SOCKET_H_