Returning correct failure code on swarmed perf test run.

testing/scripts/run_gtest_perf_test.py

Index: testing/scripts/run_gtest_perf_test.py
diff --git a/testing/scripts/run_gtest_perf_test.py b/testing/scripts/run_gtest_perf_test.py
index 5ad754e1dbc6e6cc50fd15c85db437ded9496c45..df28f6278d233df7a4f3d88561a22b472f72004e 100755
--- a/testing/scripts/run_gtest_perf_test.py
+++ b/testing/scripts/run_gtest_perf_test.py
@@ -82,7 +82,6 @@ def main():
     assert xvfb_proc and openbox_proc and xcompmgr_proc, 'Failed to start xvfb'
 
   try:
-    valid = True
     rc = 0
     try:
       executable = rest_args[0]
@@ -94,8 +93,8 @@ def main():
       else:
         executable = './%s' % executable
       with common.temporary_file() as tempfile_path:
-        valid = (common.run_command_with_output([executable] + extra_flags,
-            env=env, stdoutfile=tempfile_path) == 0)
+        rc = common.run_command_with_output([executable] + extra_flags,
+            env=env, stdoutfile=tempfile_path)
 
         # Now get the correct json format from the stdout to write to the
         # perf results file
@@ -107,8 +106,9 @@ def main():
           f.write(charts)
     except Exception:
       traceback.print_exc()
-      valid = False
+      rc = 1
 
+    valid = (rc == 0)
     failures = [] if valid else ['(entire test suite)']
     with open(args.isolated_script_test_output, 'w') as fp:
       json.dump({