Restyled the butter bar in Files.app.

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

Index: chrome/browser/resources/file_manager/css/file_manager.css
diff --git a/chrome/browser/resources/file_manager/css/file_manager.css b/chrome/browser/resources/file_manager/css/file_manager.css
index 8285b9537436cd01b87925239ebfeda94c59a520..42bdc6d789dd32a39ec7580ac2e8816f343556e1 100644
--- a/chrome/browser/resources/file_manager/css/file_manager.css
+++ b/chrome/browser/resources/file_manager/css/file_manager.css
@@ -78,7 +78,7 @@ 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;
@@ -89,7 +89,11 @@ body[new-ui] .scrollbar-vertical > .scrollbar-button.pressed {
   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;
@@ -111,7 +115,9 @@ body[new-ui] .scrollbar-vertical > .scrollbar-button.pressed {
 }
 
 body[new-ui] #butter-bar {
-  -webkit-app-region: no-drag;
+  color: #666;
+  display: -webkit-box;
+  padding: 15px;
 }
 
 #butter-bar:not(.visible) {
@@ -119,6 +125,10 @@ body[new-ui] #butter-bar {
   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;
@@ -127,6 +137,11 @@ body[new-ui] #butter-bar {
   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;
@@ -135,6 +150,10 @@ body[new-ui] #butter-bar {
   display: -webkit-box;
 }
 
+body[new-ui] #butter-bar .actions {
+  -webkit-box-align: end;
+}
+
 #butter-bar .actions a {
   color: rgb(17, 85, 204);
   cursor: pointer;
@@ -156,6 +175,10 @@ body[new-ui] #butter-bar {
   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);
 }
@@ -166,7 +189,11 @@ body[new-ui] #butter-bar {
   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;
 }