While investigating https://bugs.chromium.org/p/chromium/issues/detail?id=651574 --which was opened as a follow-up for Glimmer running out of space in September <https://bugs.chromium.org/p/chromium/issues/detail?id=650105>--I found this graph which might indicate that Glimmer is about to run out of space again:

https://chromeperf.appspot.com/report?sid=14c9f6d726af850d74c3c8fb632bffef615ffb1d62fe645470be1252a509a171&start_rev=28420000875300000&end_rev=30610000942800200