Here is a graph showing the regressions: http://graphs.mozilla.org/graph.html#tests=%5B%5B293,64,24%5D,%5B293,132,35%5D,%5B293,132,33%5D%5D&sel=1414410805648,1415015605648&displayrange=7&datatype=running I did some retriggers on tbpl: https://tbpl.mozilla.org/?tree=Fx-Team&startdate=2014-11-01&enddate=2014-11-03&jobname=Rev5%20MacOSX%20Mountain%20Lion%2010.8%20fx-team%20talos%20svgr this is the push where the TART values jump above 12 and stay in that general range: http://hg.mozilla.org/integration/fx-team/rev/c6d53703d449 Linux 32 + 64 have smaller regressions, 10.8 has the largest most pronounced regression.

The patch in question causes the js engine to register e10s-compilant interpositions for addon js compartments in single process Nightly at startup. This code needs to hang around on Nightly as long as the 'new e10s window' feature does so that new e10s windows have the proper compatibility interpositions. like new e10s window, this feature is not expected to remain Nightly only and not expected to ride the trains.

is expected to remain Nightly only*

I do not see this on mozilla-beta, can we close this?