Filter Log fieldset on admin/reports/dblog pushes the Clear Log fieldset right and produces horizontal scrollbars

Problem/Motivation

I'm seeing horizontal scrollbars on the admin/reports/dblog page, and it's because one of the collapsible fieldsets above the table of results is extending way beyond the edge of the viewport (see attached screenshot).

Reproduce by:

1. installing and enabling latest -dev of Ember as a site administration theme,
2. enabling core Database Logging (dblog) module
3. visiting admin/reports/dblog

Proposed resolution

Remove the float, display, margin-left, padding-left and width attributes from #edit-filters, which will allow both (multiple) fieldsets to sit properly in the viewport, one above the other. Either remove those declarations from sass/style.scss (currently at lines 398 and following) and recompile the css, or (hacky), remove those declarations directly from lines 1679 and following in the currently-compiled styles/style.css.

What I think is happening: On admin/reports/dblog, there are two collapsible fieldsets: one holding the form to filter the log results, and one holding the form to clear the log. The first one (css id #edit-filters) gets display: inline-block and float: left from sass/style.scss lines 398 and following, plus width: 65%. But I suspect something about how the float overrides/interacts with the display: inline-block means that the Clear Logs fieldset (with an implied width: 100%, I assume) gets pushed past the edge of the viewport, resulting in horizontal scroll bars.

Attempt at a patch to come...