We can't include MouseEventBinding.h in MouseEvents.h because that produces this include loop: MouseEventBinding.h -> UIEventBinding.h -> nsGlobalWindow.h -> nsGlobalWindowInner.h -> nsRefreshDriver.h -> AnimationEventDispatcher.h -> AnimationComparator.h -> Animation.h -> EffectCompositor.h -> PseudoElementHashEntry.h -> Element.h -> PointerEventHandler.h -> MouseEvents.h -> MouseEventBinding.h MozReview-Commit-ID: 6FNksGil7uD