This makes the "x" in the search bar always visible when there is
text in the search box, even if the mouse is not hovering, hopefully
making for a clearer UI around search and resolving issue #741
The implementation adds the "x.svg" as a background image to the search
box when it is classed with .active, in addition to the
-webkit-search-cancel-button, which is still there for the actual
functionality but only appears on mouse hover (one tiny snag is that
coloring appears slightly different on hover, at least on my screen -
don't know if this is a problem).
I accounted for both ltr and rtl text-direction by using
getComputedStyle(...).direction to detect from the input's dir="auto"
- if there's a more elegant way to do this, please suggest. An ideal
solution would use the :dir pseudo-class but it's not implemented
in Chrome yet - https://developer.mozilla.org/en-US/docs/Web/CSS/:dir
For now, I added the direction-checking to inbox_view.js. I see that
input.search is also used in new_group_update_view.js and
recipient_input_view.js but neither of these views seem to be in use (?)
and they don't set the .active class anyway, so I ignored them.
Update: Amended version a few hours later - fixed and manually tested
color and spacing for iOS and Android Dark themes. Also made some new
SASS variables to make things DRYer and fixed my tab size.
