Fixed improperly rendered error messages in gallery in Files.app.

chrome/browser/resources/file_manager/css/gallery.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. */
 
 body {
   -webkit-user-select: none;
   font-family: Open Sans, Droid Sans Fallback, sans-serif;
   font-size: 84%;
   margin: 0;
 }
@@ skipping 1037 matching lines @@
 .gallery .error-banner {
   -webkit-box-align: center;
   -webkit-box-orient: horizontal;
   -webkit-box-pack: center;
   background-color: rgba(24, 24, 24, 1);
   background-image: -webkit-image-set(
     url('../images/media/error.png') 1x,
     url('../images/media/2x/error.png') 2x);
   background-position: 25px center;
   background-repeat: no-repeat;
+  color: white;
   display: -webkit-box;
   height: 54px;
   padding-left: 70px;
   padding-right: 35px;
 }
 
 .gallery:not([error]) .error-banner {
   display: none;
 }
 
@@ skipping 194 matching lines @@
     url('../images/gallery/slideshow-pause.png') 1x,
     url('../images/gallery/2x/slideshow-pause.png') 2x);
 }
 
 .slideshow-toolbar > .slideshow-end {
   background-image: -webkit-image-set(
     url('../images/gallery/slideshow-end.png') 1x,
     url('../images/gallery/2x/slideshow-end.png') 2x);
   margin-left: -2px;
 }