Created attachment 581483 [details] [diff] [review] Patch (v1) https://tbpl.mozilla.org/?tree=Try&rev=a04daa5f7278 shows that backing out the nsDerivedSafe part of bug 666414 fixes the PGO builds on Windows.
I tried backing out this patch now that the libxul problem is solved, but I got this compilation error: e:\builds\moz2_slave\try-w32\build\obj-firefox\dist\include\nsCOMPtr.h(443) : error C3246: 'nsCOMPtr_base::nsDerivedSafe<T>' : cannot inherit from 'nsCSSStyleSheet' as it has been declared as 'sealed' This has exceeded how much I care about this problem, so I'll declare defeat here. :-)
Try run for 81fffb94b73e is complete. Detailed breakdown of the results available here: https://tbpl.mozilla.org/?tree=Try&rev=81fffb94b73e Results (out of 14 total builds): exception: 9 success: 2 failure: 3 Builds (or logs if builds failed) available at: http://firstname.lastname@example.org