`mw.eventLog.id` was introduced as part of the Better Use of Data initiative and before the Metrics Platform Clients were introduced. `mw.eventLog.id` is used to expose the user's Active Browsing Session Token. After the Metrics Platform Clients were introduced and widely adopted (spurred on by xLab / Test Kitchen), the `performer.active_browsing_session_token` contextual attribute effectively superseded the direct use of `mw.eventLog.id`. `mw.eventLog.id` should be deprecated and removed.
There are two uses of `mw.eventLog.id` that need to be tidied up:
[ ] Extension:EventLogging (1 files)
** [[https://gerrit.wikimedia.org/g/mediawiki/extensions/EventLogging/+/6147320573cc5c2d5ccc51f776ba084d136b38e8/modules/ext.eventLogging.metricsPlatform/MediaWikiMetricsClientIntegration.js|modules/ext.eventLogging.metricsPlatform/MediaWikiMetricsClientIntegration.js]] (1 matches)
NOTE: This usage **is** the definition of the `performer.active_browsing_session_token`
[ ] Extension:Wikistories (2 files)
** [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Wikistories/+/d9fd749d2bd6fe93b7f2a7c98a3feafb5a651d29/resources/instrumentation/consumptionEvents.js|resources/instrumentation/consumptionEvents.js]] (1 matches)
** [[https://gerrit.wikimedia.org/g/mediawiki/extensions/Wikistories/+/d9fd749d2bd6fe93b7f2a7c98a3feafb5a651d29/resources/instrumentation/contributionEvents.js|resources/instrumentation/contributionEvents.js]] (1 matches)