[tools/perf] Log test path in case of failure

Bug: 981349
Change-Id: I926c4ad7ba373b281e28ac99eeee2456b63fc461
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1893869Reviewed-by: Juan Antonio Navarro Pérez <perezju@chromium.org>
Commit-Queue: Mikhail Khokhlov <khokhlov@google.com>
Cr-Commit-Position: refs/heads/master@{#711685}

tools/perf/core/results_processor/util.py

@@ -62,3 +62,4 @@ def SetUnexpectedFailure(test_result):
   """Update fields of a test result in a case of processing failure."""
   test_result['status'] = 'FAIL'
   test_result['expected'] = False
+  logging.error('Processing failed for test %s', test_result['testPath'])