In an email thread ("Allowed characters in chromeperf data?"), benjhayden@ wrote this (on the topic of allowable characters in unit tests in perf data reported by Tast tests):

"I assume you're using the deprecated /add_points endpoint that accepts chartjson.
Please schedule migration to uploading HistogramSet JSON to /add_histograms using OAuth.
If you have any questions, please don't hesitate to ask or schedule a call.
If necessary, you can use chartjson2histograms, though I recommend planning to eventually modify tests to produce Histograms directly. We plan to have an implementation of Histograms for C++ and golang this year.
Units in chartjson can include slashes ("chars/s" has been used), but units in Histograms are more structured so that the frontend can format scalars more intelligently. Only these units are supported for now, including Hz and bytesPerSecond. If there's a compelling use case, then we can consider implementing more units or extending the system to support composite units."

Some links:

HistogramSet: http://doc/1vWs1KOLDfv9YC8M_xfmHViwDxDC6wEWKjkQK1-nJmNs describes HistogramSet.
chartjson2histograms: https://github.com/catapult-project/catapult/blob/master/tracing/bin/chartjson2histograms.py

I'm not sure how big of an effort switching will be, particularly the OAuth pieces. Right now, I think that Tast is just generating chartjson data, with Autotest still responsible for uploading it.

Has anyone already looked at switching Autotest to use HistogramSet?