This comment on _localizedThemeDataCacheSize was a bit garbled from getting split up, and the doc on _localizedThemeDataCache was missing from having been moved elsewhere.

It looks like the dislocation happened in 8b86d238 (#116088), which was otherwise making unrelated changes, including a couple of lines near these.  Likely it was due to an error in resolving merge or rebase conflicts at some point while revising that PR.