The initial plan was to collect CanceledAfterAppQuit histogram to understand if downloads are interrupted by clean shutdowns. Unfortunately CanceledAfterAppQuit did not show up in the logs, perhaps because UMA logging is already shut down. We need to fix CanceledAfterAppQuit and collect the data.

CanceledAfterAppQuit was logged once in M69, representing negligible number of failures caused by quitting the app. Implementing True Background Downloads will not have a visible impact on download success rate. We will pass on this feature.