We need a reliable method to wait for the Gallery app to have loaded all thumbnails. At the moment we use a combination of the appload event, checking for the expected number of thumbnails, and checking for the progress bar to be hidden. Ideally we would be able to combine the appload event with another event or dom change that indicates that the scan has completed. This existing waits can be seen here: https://github.com/mozilla/b2gperf/blob/15cbbd8441e70fd6170a268649f3f00617ba7068/b2gperf/b2gperf.py#L617

Dave, would this be different from the app-specific "ready" events proposed in bug 837633? https://bugzilla.mozilla.org/showdependencytree.cgi?id=837633&hide_resolved=1

It could be different, in that before the scan has finished the app may well be ready to use. For this bug we want to perform scroll FPS tests, so we want to be sure that all thumbnails have finished loading.

In the gaia performance measurements, we can record events sent at various moments: when the app is ready, when the app has finished rendering, etc. Main problem is that they don't currently work (see bug 912541, bug 915156 and bug 915158).

I believe this is covered by the perfomance related events such as moz-app-loaded and moz-app-visually-complete. Please reopen if this is not the case.