Make sheriff-o-matic UI be responsive to width of the window.

This makes the UI use the appropriate amount of screen real estate
at phone size widths and at larger widths. I picked 800px and 1200px
as the points to change layout. These can probably be tweaked, but
those looked good to me for now.

The only code change here that isn't just tweaking CSS or reordering
DOM nodes is moving the bugs out of ct-failure-card-buttons up into
ct-failure-stream.

NOTRY=true
R=leviw@chromium.org

Review URL: https://codereview.chromium.org/587063002

git-svn-id: svn://svn.chromium.org/blink/trunk@182555 bbb929c8-8fbe-4397-9dbb-9b2b20218538