[filebrowser] Show progress indication, while files from GData are being downloaded.

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.
  */
 
 /* Outer frame of the dialog. */
 body {
    -webkit-box-flex: 1;
    -webkit-box-orient: vertical;
@@ skipping 151 matching lines @@
   color: #42506c;
   font-size: 15px;
   font-weight: bold;
   height: 32px;
   padding-top: 8px;
   padding-bottom: 8px;
 }
 
 /* Main part of the dialog between header and footer. */
 .dialog-container {
+  position: relative;
   display: -webkit-box;
   -webkit-box-orient: horizontal;
   -webkit-box-align: stretch;
   overflow: hidden;
   -webkit-box-flex: 1;
 }
 
 /* List/grid and preview are inside this container. */
 .dialog-main {
   -webkit-box-flex: 1;
@@ skipping 221 matching lines @@
 }
 
 .dialog-container[sidebar] .dialog-body {
   -webkit-border-top-left-radius: 0;
   -webkit-border-bottom-left-radius: 0;
 }
 
 /* Container for the ok/cancel buttons. */
 .dialog-footer {
   -webkit-box-orient: horizontal;
+  -webkit-box-align: center;
   display: -webkit-box;
   margin: 15px;
   margin-top: 0;
 }
 
+.dialog-footer:not([progress]) .progress-bar,
+.dialog-footer:not([progress]) .preparing-label {
+  display: none;
+}
+
+.dialog-footer[progress] .ok,
+.dialog-footer[progress] .filename-label,
+.dialog-footer[progress] .filename-input {
+  display: none;
+}
+
+.dialog-footer .progress-bar {
+  -webkit-margin-start: 20px;
+  -webkit-margin-end: 20px;
+}
+
 /* The container for breadcrumb elements. */
 .breadcrumbs {
   -webkit-box-orient: horizontal;
   -webkit-box-flex: 1;
   -webkit-margin-end: 5px;
   display: -webkit-box;
   -webkit-box-align: center;
   line-height: 20px;
   padding-top: 1px;
   overflow: hidden;
@@ skipping 674 matching lines @@
 
 div.offline {
   -webkit-box-pack: center;
   display: -webkit-box;
 }
 
 div.offline > * {
   -webkit-box-align: center;
   display: -webkit-box;
 }
+
+div.shade {
+  position: absolute;
+  left: 0;
+  right: 0;
+  top: 0;
+  bottom: 0;
+  background-color: rgba(255, 255, 255, 0.8);
+  opacity: 0;
+  webkit-transition: opacity 1000ms linear;
+}
+
+div.shade[fadein] {
+  opacity: 1;
+}