A quick remainder that one of the biggest benefit to having our own built-in profiler is that individual teams and project can add their own performance reporting features. The graphics team just landed a feature to measure how much GPU time is consumed when compositing.
I already started using this in bug 1087530 where I used it to measure the improvement from recycling our temporary intermediate surfaces.
Currently we still haven’t completed the D3D implementation or hooked it up to WebGL, we will do that as the need arises. To implement this, when profiling, we insert a query object into the GPU pipeline for each rendering phase (framebuffer switches).