Url to the build Failure:
https://build.chromium.org/p/chromium.linux/builders/Linux Tests (dbg)(1)(32)/builds/30868

What is the bug or feature:

Regression range: https://chromium.googlesource.com/infra/infra/+log/d75632f..1afb279/appengine/findit

Non-debug view works: https://1afb279-dot-waterfall-frontend-dot-findit-for-me.appspot.com/waterfall/build-failure?url=https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20(dbg)(1)(32)/builds/30868

Debug view ran into following errors: https://1afb279-dot-waterfall-frontend-dot-findit-for-me.appspot.com/waterfall/build-failure?url=https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests%20(dbg)(1)(32)/builds/30868&debug=1


15:59:29.064
Failed to jsonify "analysis_result" defaultdict(<function <lambda> at 0x10c75f30>, {u'net_unittests on Ubuntu-12.04': defaultdict(<function <lambda> at 0x10da7770>, {'results': defaultdict(<type 'list'>, {'unclassified_failures': [{'tests': [u'EncodeValuesTest.EncodeTimeFromBeforeWindows', u'EncodeValuesTest.EncodeTimeAfterTimeTMax', <object object at 0xfb9d0070>], 'heuristic_analysis': {'suspected_cls': [{u'build_number': 30868, u'revision': u'687cf9fffda1a7eb45c80a596fa4f9e3e524f0e4', u'url': u'https://codereview.chromium.org/2091103002', u'score': 7, u'commit_position': 404708, u'hints': {u'added encode_values_unittest.cc (and it was in log)': 5, u'added encode_values.h (encode_values_unittest.cc was in log)': 1, u'added encode_values.cc (encode_values_unittest.cc was in log)': 1}, u'repo_name': u'chromium'}]}, 'supported': True, 'first_failure': 30868, 'try_job': {'status': 0, 'try_job_key': u'chromium.linux/Linux Tests (dbg)(1)(32)/30868', 'task_url': u'https://chromium-swarm.appspot.com/user/task/2ff4900362f55610', 'task_id': u'2ff4900362f55610', 'ref_name': u'net_unittests'}, 'last_pass': 30867}]})})})

NON_SWARMING=<object object at 0xfb9d0070>

File "templates/build_failure.html", line 82, in top-level template code
    findit.analysisResult = {{analysis_result | tojson | safe}};
  File "common/base_handler.py", line 25, in ToJson
    return json.dumps(data, sort_keys=True)  # Sort by key to keep order on UI.
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/__init__.py", line 250, in dumps
    sort_keys=sort_keys, **kw).encode(obj)
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/encoder.py", line 209, in encode
    chunks = list(chunks)
  ..........
  File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/encoder.py", line 184, in default
    raise TypeError(repr(o) + " is not JSON serializable")
TypeError: <object object at 0xfb9d0070> is not JSON serializable



I think it is related to https://codereview.chromium.org/2026283002