STR: 1. Run a debug build of b2g. 2. Load http://cnn.it/1H9l370 3. Scroll up and down for a while Relevant part of stack trace: Program received signal SIGSEGV, Segmentation fault. 0xb4b1d74c in mozilla::layers::ActiveElementManager::TriggerElementActivation (this=0xb1934820) at /home/botond/dev/mozilla/central/gfx/layers/apz/util/ActiveElementManager.cpp:91 91 MOZ_ASSERT(mSetActiveTask == nullptr); (gdb) i s #0 0xb4b1d74c in mozilla::layers::ActiveElementManager::TriggerElementActivation (this=0xb1934820) at /home/botond/dev/mozilla/central/gfx/layers/apz/util/ActiveElementManager.cpp:91 #1 0xb4b246b2 in mozilla::layers::APZEventState::ProcessAPZStateChange (this=this@entry=0xb193b740, aDocument=..., aViewId=<optimized out>, aChange=mozilla::layers::GeckoContentController::StartTouch, aArg=1) at /home/botond/dev/mozilla/central/gfx/layers/apz/util/APZEventState.cpp:357 #2 0xb53b4564 in mozilla::dom::TabChild::RecvNotifyAPZStateChange (this=0xb20d6400, aViewId=@0xbec9fae0: 3, aChange=@0xbec9fad4: mozilla::layers::GeckoContentController::StartTouch, aArg=@0xbec9fadc: 1) at ../../../dom/ipc/TabChild.cpp:2130

I suspect this is a regression from bug 1142437, as I can't repro it with its fix backed out.

Actually, I can't repro this at all, with or without bug 1142437, so I have no grounds to suspect it. It just seems to be very intermittent.

Forward-duping since bug 1169802 has a log