* If a search is performed in a private window and the new pref `browser.engagement.search_counts.pbm` is true, then do not record `SEARCH_COUNTS` telemetry. Note that the the pref must be true. If it's false or doesn't exist, then we record telemetry even in pbm like we normally do currently. (We record `SEARCH_COUNTS` telemetry in two places: (1) In BrowserUsageTelemetry.jsm, and (2) "in-content" telemetry directly in the search service. So skip both of those places.)
* Also skip the other ancillary telemetry recorded by `BrowserUsageTelemetry._recordSearch`: a keyed scalar and a telemetry event.
* I made some modifications to the search service to let me test the "in-content" telemetry keys
Differential Revision: https://phabricator.services.mozilla.com/D10851
747dbe936e
