Right now, the profiler instruments probes around many parts of Gecko to report "markers" in a similar way to TimelineMarkers, except these are only fetched when we fetch the profiler data. Take the TimelineMarkers "Styles" markers, compared to GeckoProfiler's "Styles" markers: http://mxr.mozilla.org/mozilla-central/source/layout/base/nsRefreshDriver.cpp#1661 Same exact place, except GeckoProfiler prefers one event over many (this may not be a concrete case, and maybe just how this was implemented), resulting in tracing code for two separate resources. Also, this leaves us with contrasting markers -- TimelineMarkers Reflow marker occurs in PresShell::DoReflow, whereas the GeckoProfilerMarker occurs in PresShell::Flush (Flush_Layout). If TimelineMarkers could use the same entry points as GeckoProfilerMarkers, then we also get way more instrumentation coverage. AFAICT, the markers[1][2] are rather similar, both having tracing meta, name, optional stack. Just TimelineMarkers require a DocShell, so that can be optional. Wouldn't it be possible to have a general marker probe where all these `profiler_tracing()` calls are, that would both call the same thing as `profiler_tracing()` now, as well as a DocShell's `AddProfileTimelineMarker()`, letting us reduce duplicate code, cover more area, and be consistent in markers? [1] http://mxr.mozilla.org/mozilla-central/source/tools/profiler/GeckoProfilerImpl.h#246 [2] http://mxr.mozilla.org/mozilla-central/source/docshell/base/TimelineMarker.h

Seems extremely unlikely the more I learn about it.