gooftool: verify release image channel

Checks release image channel is one of dev/beta/stable since those
channels support image auto-updates.

BUG=chrome-os-partner:40248
TEST=./py/system/system_unittest.py
     ./py/gooftool/gooftool_unittest.py
     gooftool verify

Change-Id: I229b8ea5f8f2b94ee8b362c881bc6bb9c39397bf
Reviewed-on: https://chromium-review.googlesource.com/273985
Commit-Queue: Bowgo Tsai <bowgotsai@chromium.org>
Tested-by: Bowgo Tsai <bowgotsai@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
diff --git a/py/gooftool/gooftool.py b/py/gooftool/gooftool.py
index fc443c9..22cc9fa 100755
--- a/py/gooftool/gooftool.py
+++ b/py/gooftool/gooftool.py
@@ -571,6 +571,17 @@
   return GetGooftool(options).VerifyBranding()
 
 
+@Command('verify_release_channel')
+def VerifyReleaseChannel(options):  # pylint: disable=W0613
+  """Verify that release image channel is correct.
+
+  ChromeOS has four channels: canary, dev, beta and stable.
+  The last three channels support image auto-updates, checks
+  that release image channel is one of them.
+  """
+  return GetGooftool(options).VerifyReleaseChannel()
+
+
 @Command('write_protect')
 def EnableFwWp(options):  # pylint: disable=W0613
   """Enable then verify firmware write protection."""
@@ -691,6 +702,7 @@
   VerifyRootFs(options)
   VerifyTPM(options)
   VerifyBranding(options)
+  VerifyReleaseChannel(options)
 
 
 @Command('untar_stateful_files')