Slice MD downloads into more components

chrome/browser/resources/md_downloads/downloads.css

-/* Copyright 2015 The Chromium Authors. All rights reserved.
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file. */
-
-body {
-  font-family: Roboto;
-}
-
-#downloads-toolbar {
-  background: rgb(63, 85, 102);
-  color: white;
-}
-
-#search-term label {
-  color: rgba(255, 255, 255, .5);
-}
-
-#search-term .label-is-highlighted label,
-#search-term input {
-  color: white;
-}
-
-#search-term .unfocused-line {
-  background-color: rgba(255, 255, 255, .5);
-}
-
-#search-term .focused-line {
-  background-color: white;
-}