Add delta update support to imaging tools.

bin/cros_run_vm_update

 #!/bin/bash
 
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 #
 # Updates an existing vm image with another image.
 
 . "$(dirname $0)/../common.sh"
 . "$(dirname $0)/../lib/cros_vm_lib.sh"
 
+DEFINE_string src_image "" \
+  "Create a delta update by passing in the image on the remote machine."
 DEFINE_string stateful_update_flag "" "Flags to pass to stateful update." s
 DEFINE_string update_image_path "" "Path of the image to update to." u
 DEFINE_string vm_image_path "" "Path of the VM image to update from." v
 
 set -e
 
 # Parse command line.
 FLAGS "$@" || exit 1
 eval set -- "${FLAGS_ARGV}"
 
 [ -n "${FLAGS_update_image_path}" ] || \
   die "You must specify a path to an image to use as an update."
 [ -n "${FLAGS_vm_image_path}" ] || \
   die "You must specify a path to a vm image."
 
 trap stop_kvm EXIT
 start_kvm "${FLAGS_vm_image_path}"
 
 $(dirname $0)/../image_to_live.sh \
   --remote=127.0.0.1 \
   --ssh_port=${FLAGS_ssh_port} \
   --stateful_update_flag=${FLAGS_stateful_update_flag} \
+  --src_image="${FLAGS_src_image}" \
   --verify \
   --image=$(readlink -f ${FLAGS_update_image_path})