Restyled the butter bar in Files.app.

chrome/browser/resources/file_manager/css/file_manager.css

 /* Copyright (c) 2012 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. */
 
 html {
   height: 100%;
 }
 
 html.col-resize * {
   cursor: col-resize !important;
@@ skipping 60 matching lines @@
 }
 
 body[new-ui] .scrollbar-vertical > .scrollbar-button:hover {
   opacity: 0.4;
 }
 
 body[new-ui] .scrollbar-vertical > .scrollbar-button.pressed {
   opacity: 0.5;
 }
 
-#butter-bar-container {
+body:not([new-ui]) #butter-bar-container {
   -webkit-box-pack: center;
   display: -webkit-box;
   left: 0;
   pointer-events: none;
   position: absolute;
   top: 0;
   width: 100%;
   z-index: 3;
 }
 
-#butter-bar {
+body[new-ui] #butter-bar-container {
+  width: 100%;
+}
+
+body:not([new-ui]) #butter-bar {
   -webkit-border-radius: 2px;
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
   -webkit-transition: opacity 130ms;
   background-color: #e3e3e3;
   border: 1px solid #d4d4d4;
   border-top-width: 0;
   color: #222;
   display: -webkit-box;
   margin-top: 2px;
   max-width: 340px;
   min-width: 200px;
   padding: 0 1em;
   pointer-events: auto;
   top: 1px;
   width: 30%;
   z-index: 2;
 }
 
 body[new-ui] #butter-bar {
-  -webkit-app-region: no-drag;
+  color: #666;
+  display: -webkit-box;
+  padding: 15px;
 }
 
 #butter-bar:not(.visible) {
   opacity: 0;
   pointer-events: none;
 }
 
+body[new-ui] #butter-bar:not(.visible) {
+  display: none;
+}
+
 #butter-bar .content {
   -webkit-box-flex: 1.0;
   -webkit-box-orient: block-axis;
   -webkit-box-pack: center;
   display: -webkit-box;
   min-height: 35px;
 }
 
+body[new-ui] #butter-bar .content {
+  -webkit-box-pack: end;
+  min-height: 0;
+}
+
 #butter-bar .actions {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: end;
   -webkit-margin-start: 6px;
   display: -webkit-box;
 }
 
+body[new-ui] #butter-bar .actions {
+  -webkit-box-align: end;
+}
+
 #butter-bar .actions a {
   color: rgb(17, 85, 204);
   cursor: pointer;
   vertical-align: middle;
 }
 
 #butter-bar .actions a.x {
   background: center center no-repeat;
   background-image: -webkit-image-set(
     url('../images/files/ui/close_bar.png') 1x,
     url('../images/files/ui/2x/close_bar.png') 2x);
   display: inline-block;
   height: 35px;  /* #butter-bar .content's min-height. */
   margin-right: -12px;
   width: 35px;
 }
 
 #butter-bar .actions a.x:first-child {
   margin-left: -6px;
 }
 
+body[new-ui] #butter-bar .actions a.x {
+  margin-bottom: -14px;
+}
+
 #butter-bar.error {
   background-color: rgba(221, 75, 57, 0.2);
 }
 
 #butter-bar .butter-message.single-line {
   overflow: hidden;
   text-overflow: ellipsis;
   white-space: nowrap;
 }
 
-#butter-bar .progress-track {
+body[new-ui] #butter-bar .butter-message.single-line {
+  line-height: 2.0;
+}
+
+body:not([new-ui]) #butter-bar .progress-track {
   height: 5px;
 }
 
 /* The top title of the dialog. */
 .dialog-title {
   -webkit-box-sizing: border-box;
   -webkit-padding-start: 15px;
   background-image: -webkit-linear-gradient(top, #fff, #f6f6f6);
   border-bottom: 1px rgb(214, 217, 227) solid;
   color: rgb(66, 80, 108);
@@ skipping 1806 matching lines @@
 }
 
 list.autocomplete-suggestions[hasElementFocus] > [selected],
 list.autocomplete-suggestions[hasElementFocus] > [lead],
 list.autocomplete-suggestions:not([hasElementFocus]) > [selected],
 list.autocomplete-suggestions:not([hasElementFocus]) > [lead] {
   background-color: rgb(238, 238, 238);
   background-image: none;
   border: 1px solid white;
 }