Fixed the disabled button to be the same size as enabled.

chrome/browser/resources/file_manager/css/common.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. */
 
 /* This file contains "borrowed" copy of standard styles. To simplify merging,
  * when altering, please preserve original property value by adding comments. */
 input.common[type='checkbox'],
 input.common[type='radio'] {
   -webkit-appearance: none;
   border: 1px solid #555;
@@ skipping 296 matching lines @@
 input[type='submit'][disabled]:hover {
   background-color: rgb(250, 250, 250);
   background-image: none;
   border: 1px solid rgb(255, 255, 255);
   border-bottom: 1px solid rgb(180, 180, 180);
   border-left: 1px solid rgb(220, 220, 220);
   border-right: 1px solid rgb(200, 200, 200);
   border-top: 1px solid rgb(220, 220, 220);
   box-shadow: inset 0 1px 1px 0 rgb(255, 255, 255);
   color: rgb(150, 150, 150);
+  padding: 2px 14px;
 }
 
 /* Gray progress bar. */
 .progress-bar {
   background-color: #e6e6e6;
   border-radius: 3px;
   height: 6px;
 }
 
 .progress-track {
@@ skipping 165 matching lines @@
   width: 44px;
 }
 
 .cr-dialog-close:hover {
   background-image: url('chrome://theme/IDR_CLOSE_DIALOG_H');
 }
 
 .cr-dialog-close:active {
   background-image: url('chrome://theme/IDR_CLOSE_DIALOG_P');
 }