According to this startup profile, PreferenceExperiments.jsm runs during startup and imports osfile.jsm. We should migrate this to the new IOUtils replacement for osfile.jsm when possible.

Stack:

(root) []
XREMain::XRE_main []
XREMain::XRE_main(int, char**, mozilla::BootstrapConfig const&) [libxul.so]
XREMain::XRE_mainRun() [libxul.so]
nsAppStartup::Run() [libxul.so]
nsBaseAppShell::Run() [libxul.so]
MessageLoop::Run() [libxul.so]
mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) [libxul.so]
nsThread::ProcessNextEvent(bool, bool*) [libxul.so]
mozilla::ipc::MessageChannel::MessageTask::Run() [libxul.so]
mozilla::ipc::MessageChannel::DispatchMessage(IPC::Message&&) [libxul.so]
mozilla::ipc::PBackgroundChild::OnMessageReceived(IPC::Message const&) [libxul.so]
PBackgroundIDBRequest::Msg___delete__ []
mozilla::dom::indexedDB::PBackgroundIDBRequestChild::OnMessageReceived(IPC::Message const&) [libxul.so]
mozilla::dom::indexedDB::BackgroundRequestChild::Recv__delete__(mozilla::dom::indexedDB::RequestResponse&&) [libxul.so]
IndexedDB:SetResultAndDispatchSuccessEvent []
mozilla::dom::indexedDB::BackgroundRequestChild::HandleResponse(nsTArray<mozilla::dom::indexedDB::SerializedStructuredCloneReadInfo>&&) [libxul.so]
mozilla::dom::indexedDB::(anonymous namespace)::detail::DispatchSuccessEvent(RefPtr<mozilla::dom::IDBRequest> const&, mozilla::SafeRefPtr<mozilla::dom::IDBTransaction> const&, RefPtr<mozilla::dom::Event> const&) [libxul.so]
mozilla::dom::EventTarget::DispatchEvent(mozilla::dom::Event&, mozilla::ErrorResult&) [libxul.so]
mozilla::DOMEventTargetHelper::DispatchEvent(mozilla::dom::Event&, mozilla::dom::CallerType, mozilla::ErrorResult&) [libxul.so]
mozilla::EventDispatcher::DispatchDOMEvent(nsISupports*, mozilla::WidgetEvent*, mozilla::dom::Event*, nsPresContext*, nsEventStatus*) [libxul.so]
EventDispatcher::Dispatch []
EventDispatcher::Dispatch success []
mozilla::EventDispatcher::Dispatch(nsISupports*, nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event*, nsEventStatus*, mozilla::EventDispatchingCallback*, nsTArray<mozilla::dom::EventTarget*>*) [libxul.so]
mozilla::EventTargetChainItem::HandleEventTargetChain(nsTArray<mozilla::EventTargetChainItem>&, mozilla::EventChainPostVisitor&, mozilla::EventDispatchingCallback*, mozilla::ELMCreationDetector&) [libxul.so]
mozilla::EventListenerManager::HandleEventInternal(nsPresContext*, mozilla::WidgetEvent*, mozilla::dom::Event**, mozilla::dom::EventTarget*, nsEventStatus*, bool) [libxul.so]
<name omitted> [libxul.so]
promise callback []
mozilla::PromiseJobRunnable::Run(mozilla::AutoSlowOperation&) [libxul.so]
mozilla::dom::PromiseJobCallback::Call(mozilla::dom::BindingCallContext&, JS::Handle<JS::Value>, mozilla::ErrorResult&) [libxul.so]
JS::Call(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, JS::HandleValueArray const&, JS::MutableHandle<JS::Value>) [libxul.so]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
PromiseReactionJob(JSContext*, unsigned int, JS::Value*) [libxul.so]
AsyncFunctionResume(JSContext*, JS::Handle<js::AsyncFunctionGeneratorObject*>, ResumeKind, JS::Handle<JS::Value>) [libxul.so]
js::CallSelfHostedFunction(JSContext*, JS::Handle<js::PropertyName*>, JS::Handle<JS::Value>, js::AnyInvokeArgs const&, JS::MutableHandle<JS::Value>) [libxul.so]
js::Call(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, js::AnyInvokeArgs const&, JS::MutableHandle<JS::Value>, js::CallReason) [libxul.so]
js::RunScript []
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
AsyncFunctionNext [self-hosted:688:26]
0xff4eaa5ea9f []
js::jit::InterpretResume(JSContext*, JS::Handle<JSObject*>, JS::Value*, JS::MutableHandle<JS::Value>) [libxul.so]
js::CallSelfHostedFunction(JSContext*, JS::Handle<js::PropertyName*>, JS::Handle<JS::Value>, js::AnyInvokeArgs const&, JS::MutableHandle<JS::Value>) [libxul.so]
js::Call(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, js::AnyInvokeArgs const&, JS::MutableHandle<JS::Value>, js::CallReason) [libxul.so]
js::RunScript []
InterpretGeneratorResume [self-hosted:1146:33]
recordOriginalValues [resource://normandy/lib/PreferenceExperiments.jsm:218:28]
> ensureStorage [resource://normandy/lib/PreferenceExperiments.jsm:149:22]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
Interpret(JSContext*, js::RunState&) [libxul.so]
js::NativeGetExistingProperty(JSContext*, JS::Handle<JSObject*>, JS::Handle<js::NativeObject*>, JS::Handle<js::Shape*>, JS::MutableHandle<JS::Value>) [libxul.so]
js::CallGetter(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, JS::MutableHandle<JS::Value>) [libxul.so]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
mozilla::dom::module_getter::ModuleGetter(JSContext*, unsigned int, JS::Value*) [libxul.so]
mozJSComponentLoader::Import(JSContext*, nsTSubstring<char> const&, JS::MutableHandle<JSObject*>, JS::MutableHandle<JSObject*>, bool) [libxul.so]
profiler_get_backtrace() [libxul.so]
Registers::SyncPopulate() [libxul.so]

https://hg.mozilla.org/mozilla-central/rev/42f9d968a9a9