toggle normalization & zoom on/off
and wire it all up to a pref that re-renders upon change.
separately, make a few improvements to whitespace management
when zoomed in with normalized mode:
* place attachment overlays at the top of their regions
* place overlays above the first expanded message at the top of
the conversation, instead of the usual position just above the
message.
* impose a max zoom factor to limit excessive spacer whitespace
Bug: 7312540
Change-Id: Iae3afff0ee81e4ba9367568e884a041780b24ebf
12 files changed