M59: Revert of "Replace homebrew scrollbar in Files app with that of Blink."

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

Index: ui/file_manager/file_manager/foreground/css/file_manager.css
diff --git a/ui/file_manager/file_manager/foreground/css/file_manager.css b/ui/file_manager/file_manager/foreground/css/file_manager.css
index bc8483a0c9c97517e7c228d3c0ed751dbe37e420..eb9b5f7e2a439765c76fb606f217e78f20fb9e31 100644
--- a/ui/file_manager/file_manager/foreground/css/file_manager.css
+++ b/ui/file_manager/file_manager/foreground/css/file_manager.css
@@ -60,6 +60,50 @@ a:focus {
   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;
@@ -959,6 +1003,12 @@ html[dir='rtl'] .breadcrumbs .separator {
   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);