Make images center aligned after distillation

components/dom_distiller/core/css/distilledpage.css

 /* Copyright 2014 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. */
 
 /* Set the global 'box-sizing' state to 'border-box'.
  * *::after and *::before used to select pseudo-elements not selectable by *. */
 
 *,
 *::after,
 *::before {
@@ skipping 345 matching lines @@
 object,
 video {
   max-width: 100%;
 }
 
 /* TODO(sunangel): make images zoomable. */
 
 img {
   display: block;
   height: auto;
-  margin: 0.6rem auto 0.4rem 0;
+  margin: 0.6rem auto 0.4rem auto;
 }
 
 /* TODO(nyquist): set these classes directly in the dom distiller. */
 
 embed+[class*='caption'],
 figcaption,
 img+[class*='caption'],
 object+[class*='caption'],
 video+[class*='caption'] {
   opacity: .8;
@@ skipping 116 matching lines @@
 }
 
 .youtubeIframe {
   height: 100%;
   left: 0px;
   position: absolute;
   top: 0px;
   width: 100%;
 }