[autotest] Support firmware_ro_build_spec in suite scheduler.

This change allows user to specify firmware_ro_build_spec in suite
scheduler ini file. Suite scheduler will create suite jobs based on the
given RO firmware build spec.

BUG=chromium:575394
TEST=local run
/usr/local/autotest/site_utils/suite_scheduler/suite_scheduler.py \
  -d /usr/local/autotest/logs -f /usr/local/autotest/ss_test.ini  \
  -e nightly  -i veyron_jerry-release/R49-7834.3.0 \
  -r /tmp/_autotmp_0pjXWQ_suite_scheduler

test task:
[FaftEcNightly]
run_on: nightly
suite: dummy
branch_specs: ==tot-2
firmware_rw_build_spec: firmware
firmware_ro_build_spec: firmware
test_source: cros

Change-Id: Ib453ccee6c95a10570c692f0280513c8d78e3173
Reviewed-on: https://chromium-review.googlesource.com/329931
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Dan Shi <dshi@google.com>
diff --git a/frontend/afe/site_rpc_interface.py b/frontend/afe/site_rpc_interface.py
index 01fb48e..ac7e9a4 100644
--- a/frontend/afe/site_rpc_interface.py
+++ b/frontend/afe/site_rpc_interface.py
@@ -200,11 +200,7 @@
     # R45 falls out of stable channel.
     if build and not builds:
         builds = {provision.CROS_VERSION_PREFIX: build}
-    # TODO(dshi): crbug.com/497236 Remove this check after firmware ro provision
-    # is supported in Autotest.
-    if provision.FW_RO_VERSION_PREFIX in builds:
-        raise error.SuiteArgumentException(
-                'Updating RO firmware is not supported yet.')
+
     # Default test source build to CrOS build if it's not specified and
     # run_prod_code is set to False.
     if not run_prod_code: