MetricController.track & Event.wrapper may use non-trivial power: called frequently

[mcomella]

MetricController.track calls the Event.wrapper method, which is a long chain of comparisons, twice to submit telemetry. To test the impact of these methods, I did a simple workflow:

• click wiki homescreen
• click url bar, nav amazon.com
• click tabs tray, new tab
• search "foobar" and click default search result

I added custom markers and took profiles:

• Event.wrapper: https://share.firefox.dev/3lipdoU
• MetricController.track: https://share.firefox.dev/2Xha5QD (the profiler marker is misnamed GleanMetricsService)

In these profiles of this simple workflow, we see:

• MetricController.track is called 19 times for a total duration of 57.3ms
• Event.wrapper is called 36 times for a total of 24.3ms (I believe this is a subset of MetricController)
• (caveat: these duration may be inflated because these calls are fast and clock granularity might not be good enough)
• (note: I used window.filteredMarkers.map((m) => m.end - m.start).reduce((acc, i) => acc + i) to measure this)

These durations will be unnoticeable to the user, however, they will use battery. wrt Event.wrapper, this doesn't need to be a long chain of comparisons – perhaps by calling the Glean API directly and removing MetricController – so we can stop the users' device from doing work it doesn't need to. We should investigate MetricController for similar wins.

wrt prioritization, there may be larger gains we can do to improve battery life (e.g. #15921) but those are likely harder to implement so it could be worth addressing this issue.

Note: #19967 may also address this issue.

[mcarare]

This issue will serve as a meta. I will link here the issues handling the removal of the wrapper in separate components. This will make QA work easier and ensure we do not have regressions by tackling the whole work in smaller pieces.

[mcarare]

• Remove wrapper for Tabs Tray telemetry #24098
• Remove wrapper for Collections telemetry #24099
• Remove wrapper from search widget metrics. #24147
• Remove wrapper for ETP metrics. #24148
• Remove wrapper for onboarding metrics #24203
• Remove wrapper for search_shortcuts metrics #24204
• Remove wrapper for toolbar menu clicked in default browser experiment #24205
• Remove wrapper for context menu metrics  #24206
• Remove wrapper for toolbar settings metrics  #24207
• Remove wrapper for login dialog #24208
• Remove wrapper for home customization settings metrics #24209
• Remove wrapper for metrics in the "events" category #24210
• Remove wrapper for metrics in the "metrics" category #24211
• Remove wrapper for preferences (settings) metrics #24212
• Remove wrapper for search.default_engine #24213
• Remove wrapper for bookmarks management #24214
• Remove wrapper for custom tabs metrics #24215

[mcarare]

This can be closed as all MetricController.track and Event.wrapper usages have been removed from the app.