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* Improve `Header` performance a bit I have been investigating `<Header />` component performance once again today with `render` cycles in particular. I have observed that during `push` phase, a typical Header in NavigationPlayground re-renders 3 times on iOS and 2 times on Android. The first time is obvious on both platforms since that's when we add a new scene to an array. Second on iOS was also self-explanatory - we measure title width and other layout parameters in order to provide a better animation. What got me thinking was the last render cycle that didn't have a clear origin. After digging around I've found it is caused by a `scenes` array changing when transition finishes. What is surprising, it's just the reference to the object that changes, the content (items inside) stay the same. I have found out that this is caused by `Transitioner` looping through an array of scenes attempting to remove stale scenes. Since scene becomes stale when you `pop` from it, this is obviously a noop when `pushing` a new route. That, obviously, causes an extra render cycle since `filter` produces same, but with a different pointer, object. * Update Transitioner.js * Update Transitioner.js