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

mojo/devtools/common/mojo_benchmark

Index: mojo/devtools/common/mojo_benchmark
diff --git a/mojo/devtools/common/mojo_benchmark b/mojo/devtools/common/mojo_benchmark
index 8f83c5be4ef87c84ae84327a6e248e1043bbb702..ec17ad0fc52a1fbce22f015f430614e1ff4f9dfd 100755
--- a/mojo/devtools/common/mojo_benchmark
+++ b/mojo/devtools/common/mojo_benchmark
@@ -228,11 +228,12 @@ def main():
         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