When the code breaks in the browser, we should notice that it is broken to fix it ASAP. Now we don't.
* [Module that captures errors in core](https://github.com/wikimedia/mediawiki/blob/master/resources/src/mediawiki/mediawiki.errorLogger.js)
* [How it is done in #uploadwizard](https://github.com/wikimedia/mediawiki-extensions-UploadWizard/blob/58a31927b0408ba6b284e433843ab15f8bf42e4a/resources/uw.EventFlowLogger.js#L188-L226)
* JS exceptions
* ResourceLoader errors
==AC
[] Setup [the MobileFrontendException schema](https://meta.wikimedia.org/wiki/Schema:MobileFrontendException) for capturing errors using [[ https://meta.wikimedia.org/wiki/Schema:UploadWizardExceptionFlowEvent | UploadWizardExceptionFlowEvent ]] as inspiration.
[] JS window errors are captured via `mw.trackSubscribe( 'global.error' )` and logged to the event logging schema using `mw.track( 'event.MobileFrontendExceptionEvent' )` or a `mw.eventLogging.Schema` class
[] We have informed ourselves of how we'll make use of sentry at some point when it is ready and if we can help move the project forward
[] We have a configurable sampling rate for this instrumentation, which has a sensible sampling rate so that we don't break production when there is a widespread error. Suggested initial value: 0.01 of pageviews.
[] Should be feature flagged, defaulting to false (we'll enable on one wiki)
[] This should be done in WikimediaEvents