* make shouldCancelNavigationBack a var
* rename OWSNavigationView->OWSNavigationChildController
* forward delegate calls to OWSNavigationController
* apply theme and style to OWSNavigationBar consistently
fix themeing on gif picker controller
* Use topPinned navbar position. Size the blur effect view using the background view
* Use fade animation when hiding the navigation bar
* fix issues with reduced transparency setting
* pr feedback
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