Leave 20px for iOS status bar background. Fix selector for view caching.

[rossmartin]

This PR resolves the issue where the header bar shrinks the whole 64px rather than 44 on iOS and does not leave a background for the status bar (because the status bar overlays the web view). I realize you can use StatusBar.overlaysWebView(false) but this results in unnecessary real estate in the header bar. If you watch the video in this article on devdactic Shrinking Headers Like Facebook With the Ionic Framework you will notice the extra space in the header bar and it looks funky.

I also removed the shrink function at the top because it is not being used anywhere in the directive.

[pliablepixels]

@rossmartin --> have you tried this with https://github.com/djett41/ionic-scroll-sista ? That repo looks to be more stable than this. I implemented your changes - while it works, when I scroll up there is a lot of flicker. My changed version https://gist.github.com/pliablepixels/5a08bd8c40e5123f0379c32d3370ea81

[pliablepixels]

@rossmartin - never mind - fixed the problem - if/then/else issue in my code

[AshleyDeng]

Hi @pliablepixels

Can you post your most updated solution? I integrated your previous solution and I have a lot of flickers too.

Thanks!
Ash

[pliablepixels]

@AshleyDeng - I switched to ionic scroll sista and modified it (including Ross' tweak) to meet my needs instead.