mojo_benchmark: return non-zero exit code when --upload fails.

mojo/devtools/common/mojo_benchmark

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Runner for Mojo application benchmarks."""
 
 import argparse
 import logging
 import os.path
@@ skipping 210 matching lines @@
           print 'benchmark failed: ' + benchmark_error
         if some_measurements_failed:
           print 'some measurements failed'
         print 'output: '
         print '-' * 72
         print output
         print '-' * 72
         exit_code = 1
 
       if script_args.upload:
-        perf_dashboard.upload_chart_data(
+        if not perf_dashboard.upload_chart_data(
             script_args.master_name, script_args.bot_name,
             script_args.test_name, script_args.builder_name,
             script_args.build_number, chart_data_recorder.get_chart_data(),
-            script_args.server_url, script_args.dry_run)
+            script_args.server_url, script_args.dry_run):
+          exit_code = 1
 
   return exit_code
 
 if __name__ == '__main__':
   sys.exit(main())