Url to the build Failure:
https://build.chromium.org/p/chromium.mac/builders/Mac10.9 Tests (dbg)/builds/26972

What is the bug or feature:

Search for "_RetrieveOutputJsonFile" on waterfall-backend will show more.

Traceback (most recent call last):
  File "third_party/pipeline_utils/appengine_third_party_pipeline_python_src_pipeline/pipeline.py", line 2158, in evaluate
    self, pipeline_key, root_pipeline_key, caller_output)
  File "third_party/pipeline_utils/appengine_third_party_pipeline_python_src_pipeline/pipeline.py", line 1113, in _run_internal
    return self.run(*self.args, **self.kwargs)
  File "waterfall/detect_first_failure_pipeline.py", line 465, in run
    master_name, builder_name, build_number, failed_steps, builds)
  File "waterfall/detect_first_failure_pipeline.py", line 366, in _CheckFirstKnownFailureForSwarmingTests
    failed_step, http_client)
  File "waterfall/detect_first_failure_pipeline.py", line 224, in _StartTestLevelCheckForFirstFailure
    list_isolated_data, http_client)
  File "waterfall/swarming_util.py", line 345, in RetrieveShardedTestResultsFromIsolatedServer
    output_json = _DownloadTestResults(isolated_data, http_client)
  File "waterfall/swarming_util.py", line 282, in _DownloadTestResults
    output_json_content, http_client)
  File "waterfall/swarming_util.py", line 255, in _RetrieveOutputJsonFile
    return json.loads(zlib.decompress(get_content)) if get_content else None
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/decoder.py", line 365, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/decoder.py", line 383, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded