Verify that new DOM properties are really disabled
We have the following DOM objects that were not present in esr31: onlanguagechange, mozRequestOverfill, back, forward, home, openDialog, controllers, realFrameElement, MozSelfSupport, _content, Symbol, WeakSet, HTMLPictureElement, AnimationEffect, PerformanceMeasure, PluginCrashedEvent, MenuBoxObject, ScrollViewChangeEvent, SelectionStateChangedEvent, DOMMatrixReadOnly, DOMMatrix, PopupBoxObject, AnimationTimeline, PerformanceMark, DOMApplication, IDBMutableFile, StereoPannerNode, CameraDetectedFace, CameraStateChangeEvent, CSSCounterStyleRule, CameraRecorderVideoProfile, CameraRecorderProfile, CameraRecorderProfiles, AnonymousContent, NamedNodeMap, DOMApplicationsManager, ContentProcessMessageManager, CameraConfigurationEvent, HTMLAllCollection, PromiseDebugging, SubtleCrypto, Animation, CameraRecorderAudioProfile, RadioNodeList, WindowRoot, CameraClosedEvent, CryptoKey, CameraFacesDetectedEvent, MozSettingsTransactionEvent, IDBFileRequest, BroadcastChannel, MessageChannel, AnimationPlayer
Some of those should have been disabled by various prefs we have set (in particular PerformanceMeasure, PerformanceMark, and the IDB objects). We should look into that. Hopefully they are just empty placeholders. Also, the camera stuff should have been compiled out and also disabled via the peerconnection prefs, I thought.