Update paycheck to understand the updated update_metadata fields.

When checking a payload, always start by printing a description of the
payload being checked.

Recompiled (with protoc) the updated update_metadata.proto from the
update_engine.

BUG=chromium:226310
TEST=Manual Run
CQ-DEPEND=CL:47347

Change-Id: Ib60c6e6978d30444db7b65ef6d09540c9ffacdb8
Reviewed-on: https://gerrit.chromium.org/gerrit/50899
Commit-Queue: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Tested-by: Don Garrett <dgarrett@chromium.org>
diff --git a/scripts/paycheck.py b/scripts/paycheck.py
index 9689af4..9852ded 100755
--- a/scripts/paycheck.py
+++ b/scripts/paycheck.py
@@ -59,6 +59,8 @@
   check_opts.add_option('-c', '--check', action='store_true', default=False,
                         help=('force payload integrity check (e.g. before '
                               'applying)'))
+  check_opts.add_option('-D', '--describe', action='store_true', default=False,
+                        help='Print a friendly description of the payload.')
   check_opts.add_option('-r', '--report', metavar='FILE',
                         help="dump payload report (`-' for stdout)")
   check_opts.add_option('-t', '--type', metavar='TYPE', dest='assert_type',
@@ -175,6 +177,9 @@
       # Initialize payload.
       payload.Init()
 
+      if options.describe:
+        payload.Describe()
+
       # Perform payload integrity checks.
       if options.check:
         report_file = None