Replace homebrew scrollbar in Files app with that of Blink.

ui/file_manager/file_manager/foreground/css/file_manager.css

 /* Copyright (c) 2014 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. */
 
 /* Special attribute used in HTML to hide elements. */
 body:not([type]) [visibleif] {
   display: none;
 }
 
 body[type='folder'] [invisibleif~='folder'],
@@ skipping 42 matching lines @@
 a:focus {
   outline-color: rgb(77, 144, 254);
 }
 
 /* Drop opacity of selected rows to give a visual feedback on copy/cut
  * operation. */
 .blink {
   opacity: 0.8;
 }
 
-.dialog-container ::-webkit-scrollbar {
-  height: 0;
-  width: 0;
-}
-
-/* TODO(mtomasz): Flip scrollbars to the opposite side for RTL languages. */
-.scrollbar-vertical {
-  bottom: 0;
-  flex: none;
-  pointer-events: none;
-  position: absolute;
-  right: 0;
-  top: 0;
-  width: 10px;
-  z-index: 500;  /* Must be below the contextmenu (600). */
-}
-
-.scrollbar-button {
-  background-color: black;
-  border-radius: 3px;
-  border: 1px solid #ccc;
-  box-sizing: border-box;
-  height: 50%;
-  margin-right: 2px;
-  opacity: 0;
-  pointer-events: auto;
-  position: absolute;
-  transition: opacity 100ms;
-  width: 8px;
-}
-
-:hover > .scrollbar-vertical > .scrollbar-button,
-.scrollbar-vertical > .scrollbar-button.scrolling {
-  opacity: 0.3;
-}
-
-.scrollbar-vertical > .scrollbar-button:hover {
-  opacity: 0.4;
-}
-
-.scrollbar-vertical > .scrollbar-button.pressed {
-  opacity: 0.5;
-}
-
 /* Main part of the dialog between header and footer. */
 .dialog-container {
   align-items: stretch;
   background-color: rgb(250, 250, 250);  /* Makes #drag-container invisible. */
   display: flex;
   flex: auto;
   flex-direction: row;
   overflow: hidden;
   position: relative;
 }
@@ skipping 879 matching lines @@
   flex: auto;
   flex-direction: column;
   min-height: 0;
 }
 
 #detail-table > list,
 .thumbnail-grid {
   flex: auto;
 }
 
-#file-list {
-  /* Override overflow specifying by table_list.js to use the original scroll
-     bar. crbug.com/391698 */
-  overflow: scroll !important;
-}
-
 #file-list .drag-selection-border {
   -webkit-box-sizing: border-box;
   background-color: rgba(255, 255, 255, 0.3);
   border: 2px solid rgba(255, 255, 255, 0.6);
   outline: 1px solid rgba(0, 0, 0, 0.1);
   position: absolute;
   z-index: 2;
 }
 
 .spinner {
@@ skipping 1258 matching lines @@
   border-radius: 2px;
   color: white;
   display: none;  /* hidden until activaed */
   font-size: 12px;
   height: 24px;
   line-height: 24px;
   padding: 0 8px;
   position: absolute;
   z-index: 1000;  /* same height as files-tooltip */
 }