Removed the OK button from the action choice dialog.

chrome/browser/resources/file_manager/css/action_choice.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. */
 
 input:focus,
 button:focus {
   outline-color: rgb(77, 144, 254);
 }
 
 .action-choice {
@@ skipping 103 matching lines @@
   -webkit-user-drag: none;
   position: absolute;
 }
 
 .counter {
   color: #808080;
   margin: 5px 3px;
   width: 100%;
 }
 
-.footer {
-  -webkit-box-orient: horizontal;
-  -webkit-box-pack: end;
-  bottom: 0;
-  display: -webkit-box;
-  left: 0;
-  position: absolute;
-  right: 0;
-}
-
-.footer button {
-  height: 27px;
-  margin-left: 10px;
-  min-width: 80px;
-}
-
 .choices {
   width: 100%;
 }
 
 /* Padding counterweights negative margins of items, thus eliminating scroll
    bar when it's not needed. Max height is set to fit 8 items before showing
    scroll bar. */
 #actions-list {
   display: block;
   max-height: 328px;
@@ skipping 47 matching lines @@
   background-image: -webkit-image-set(
     url('../images/icon32.png') 1x,
     url('../images/icon64.png') 2x);
 }
 
 #actions-list > li > div.watch-single-video {
   background-image: -webkit-image-set(
     url('../images/media/watch.png') 1x,
     url('../images/media/2x/watch.png') 2x);
 }