Caused by: "Separate all refactor code for downloads as a foreground service."
Commit: 94298d7de8ab29bc0d95970137e4c52886ca1771

Link to size graph: https://chromeperf.appspot.com/report?sid=a097e74b1aa288511afb4cb616efe0f95ba4d347ad61d5e835072f23450938ba&num_points=10&rev=498445
(Note: point has many commits, but used diagnose_bloat.py to identify this commit).

Debugging size regressions is documented at: https://chromium.googlesource.com/chromium/src/+/master/docs/speed/apk_size_regressions.md#Debugging-Apk-Size-Increase

Looks like the growth was entirely from dex growth. Checked dex diff, and there's doesn't seem to be any unexpected classes/methods pulled in (size growth is from the large change). 

Feel free to close as “Won't Fix” unless you can see some way to reduce size.