Seeing the following:

Traceback (most recent call last):
  File "/mnt/data/b/rr/tmpAomefP/rw/checkout/scripts/slave/recipe_modules/test_results/resources/upload_test_results.py", line 216, in <module>
    sys.exit(main(sys.argv[1:]))
  File "/mnt/data/b/rr/tmpAomefP/rw/checkout/scripts/slave/recipe_modules/test_results/resources/upload_test_results.py", line 207, in main
    options.test_results_server, attrs, files, 120)
  File "/mnt/data/b/rr/tmpAomefP/rw/checkout/scripts/slave/recipe_modules/test_results/resources/test_results_uploader.py", line 51, in upload_test_results
    timeout_secs)
  File "/mnt/data/b/rr/tmpAomefP/rw/checkout/scripts/slave/recipe_modules/test_results/resources/test_results_uploader.py", line 135, in _retry_exp_backoff
    % (e.code, e.filename, e.read()))
test_results_uploader.PermanentError: Received HTTP status 400 loading "https://test-results.appspot.com/testfile/upload": strconv.Atoi: parsing "null": invalid syntax

This appears to be affecting uploads to the the production instance across a variety of bots, e.g.

  https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests/67486
  https://ci.chromium.org/buildbot/chromium.win/Win7%20Tests%20%281%29/77169
  https://ci.chromium.org/buildbot/chromium.mac/Mac10.9%20Tests/54047

This appears to be the same error we saw on the staging instance in https://bugs.chromium.org/p/chromium/issues/detail?id=812332