Revert "cros_generate_update_payload: kill old style update image generation"

cros_generate_update_payload

Index: cros_generate_update_payload
diff --git a/cros_generate_update_payload b/cros_generate_update_payload
index 586b2f8f2396640e54f93e7755e3407b848c38ab..b55f438526109e2db548938d8d5b588a5ede0ec9 100755
--- a/cros_generate_update_payload
+++ b/cros_generate_update_payload
@@ -247,11 +247,6 @@ if [ "$DELTA" -eq "$FLAGS_TRUE" -o "$FLAGS_old_style" -eq "$FLAGS_FALSE" ]; then
 else
   echo "Generating old-style full update"
 
-  # TODO(zbehan): Remove this branch entirely and disable the cmdline option.
-  echo "This is a deprecated and unused behaviour. It also introduces unwanted"
-  echo "dependency to a third script (mk_memento_images) which has become broken."
-  exit 1
-
   trap cleanup INT TERM EXIT
   DST_KERNEL=$(extract_partition_to_temp_file "$FLAGS_image" 2)
   if [ "$FLAGS_patch_kernel" -eq "$FLAGS_TRUE" ]; then
@@ -259,7 +254,7 @@ else
   fi
   DST_ROOT=$(extract_partition_to_temp_file "$FLAGS_image" 3)
 
-#  GENERATOR="${SCRIPTS_DIR}/mk_memento_images.sh"
+  GENERATOR="${SCRIPTS_DIR}/mk_memento_images.sh"
 
   CROS_GENERATE_UPDATE_PAYLOAD_CALLED=1 "$GENERATOR" "$DST_KERNEL" "$DST_ROOT"
   mv "$(dirname "$DST_KERNEL")/update.gz" "$FLAGS_output"