Merge "Add a system property to init that drops caches." am: 12744bd2

on property:sys.sysctl.extra_free_kbytes=*

    write /proc/sys/vm/extra_free_kbytes ${sys.sysctl.extra_free_kbytes}

# Allow users to drop caches

on property:perf.drop_caches=3

    write /proc/sys/vm/drop_caches 3

    setprop perf.drop_caches 0

# "tcp_default_init_rwnd" Is too long!

on property:net.tcp_def_init_rwnd=*

    write /proc/sys/net/ipv4/tcp_default_init_rwnd ${net.tcp_def_init_rwnd}