Expose the return code for gpu tests in bb_run_bot.

build/android/buildbot/bb_utils.py

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import json
 import optparse
 import os
 import subprocess
 import sys
 
@@ skipping 78 matching lines @@
   return ['--factory-properties=%s' % json.dumps(options.factory_properties),
           '--build-properties=%s' % json.dumps(options.build_properties)]
 
 
 def RunSteps(steps, step_cmds, options):
   unknown_steps = set(steps) - set(step for step, _ in step_cmds)
   if unknown_steps:
     print >> sys.stderr, 'FATAL: Unknown steps %s' % list(unknown_steps)
     sys.exit(1)
 
+  exit_code = 0
   for step, cmd in step_cmds:
     if step in steps:
-      cmd(options)
+      exit_code = cmd(options) or exit_code
+
+  return exit_code