init.rc: prep tcp_default_init_rwnd, set the default to 60

The kernel's default is between 4~20.

Prepare for javaland to modify the value at runtime.

It can be done via
  setprop sys.sysctl.tcp_def_init_rwnd  <value>


Bug: 12020135
Change-Id: Id34194b085206fd02e316401c0fbbb9eb52522d2
(cherry picked from commit 7c862c8b)

rootdir/init.rc

@@ -369,6 +369,9 @@ on boot
     setprop net.tcp.buffersize.gprs    4092,8760,11680,4096,8760,11680
     setprop net.tcp.buffersize.evdo    4094,87380,262144,4096,16384,262144
 
+# Define default initial receive window size in segments.
+    setprop net.tcp.default_init_rwnd 60
+
     class_start core
     class_start main
 
@@ -401,9 +404,15 @@ on property:vold.decrypt=trigger_shutdown_framework
 on property:sys.powerctl=*
     powerctl ${sys.powerctl}
 
-# system server cannot write to /proc/sys files, so proxy it through init
+# system server cannot write to /proc/sys files,
+# and chown/chmod does not work for /proc/sys/ entries.
+# So proxy writes through init.
 on property:sys.sysctl.extra_free_kbytes=*
     write /proc/sys/vm/extra_free_kbytes ${sys.sysctl.extra_free_kbytes}
+# "tcp_default_init_rwnd" Is too long!
+on property:sys.sysctl.tcp_def_init_rwnd=*
+    write /proc/sys/net/ipv4/tcp_default_init_rwnd ${sys.sysctl.tcp_def_init_rwnd}
+
 
 ## Daemon processes to be run by init.
 ##