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

R=qsr@chromium.org

Review URL: https://codereview.chromium.org/1405223009 .

Cr-Mirrored-From: https://github.com/domokit/mojo
Cr-Mirrored-Commit: e04476df3b28935dd62b5912f3c7a00c59ffe5e6

mojo_benchmark

diff --git a/mojo_benchmark b/mojo_benchmark
index 8f83c5b..ec17ad0 100755
--- a/mojo_benchmark
+++ b/mojo_benchmark
@@ -228,11 +228,12 @@
         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