Gallery: Editor: View full picture when applying filters

* Current behaviour: Edit picture (e.g. crop) -> top of pic is hidden by
  action bar
* New behaviour: Picture is fully visible

Test: manual
Fixes: https://gitlab.com/LineageOS/issues/android/issues/1435
Change-Id: I2aa2281e976622cdbd0145d3895c36e4b21bdc7d