According to this startup profile, ContentPrefService2.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]
IdleRequestExecutor::Run() [libxul.so]
nsGlobalWindowInner::ExecuteIdleRequest(mozilla::TimeStamp) [libxul.so]
<name omitted> [libxul.so]
requestIdleCallback handler []
mozilla::dom::IdleRequest::IdleRun(nsPIDOMWindowInner*, double, bool) [libxul.so]
mozilla::dom::IdleRequestCallback::Call(mozilla::dom::BindingCallContext&, JS::Handle<JS::Value>, mozilla::dom::IdleDeadline&, 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::RunScript []
idleTaskRunner [chrome://browser/content/browser.js:2257:49]
_schedulePerWindowIdleTasks/< [chrome://browser/content/browser.js:2323:27]
maybeCreatePreloadedBrowser [resource:///modules/NewTabPagePreloading.jsm:115:29]
FullZoom_onLocationChange [chrome://browser/content/browser-fullZoom.js:216:54]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
Interpret(JSContext*, js::RunState&) [libxul.so]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
XPC_WN_CallMethod(JSContext*, unsigned int, JS::Value*) [libxul.so]
XPCWrappedNative::CallMethod(XPCCallContext&, XPCWrappedNative::CallMode) [libxul.so]
NS_InvokeByIndex [libxul.so]
SharedStub [libxul.so]
PrepareAndDispatch [libxul.so]
XPCWrappedJS method call []
nsXPCWrappedJS::CallMethod(unsigned short, nsXPTMethodInfo const*, nsXPTCMiniVariant*) [libxul.so]
JS_CallFunctionValue(JSContext*, JS::Handle<JSObject*>, JS::Handle<JS::Value>, JS::HandleValueArray const&, JS::MutableHandle<JS::Value>) [libxul.so]
js::RunScript []
CPS2_getByDomainAndName [resource://gre/modules/ContentPrefService2.jsm:212:54]
CPS2__get [resource://gre/modules/ContentPrefService2.jsm:236:26]
CPS2__execStmts [resource://gre/modules/ContentPrefService2.jsm:908:44]
js::InternalCallOrConstruct(JSContext*, JS::CallArgs const&, js::MaybeConstruct, js::CallReason) [libxul.so]
Interpret(JSContext*, js::RunState&) [libxul.so]
<name omitted> [libxul.so]
js::CallGetter(JSContext*, JS::Handle<JS::Value>, JS::Handle<JS::Value>, JS::MutableHandle<JS::Value>) [libxul.so]
js::RunScript []
get conn [resource://gre/modules/ContentPrefService2.jsm:137:10]
get conn/this._connPromise< [resource://gre/modules/ContentPrefService2.jsm:142:39]
> _getConnection [resource://gre/modules/ContentPrefService2.jsm:1167:22]
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/5c8f76f41e4e