User pods centered with any resolution.

chrome/browser/resources/chromeos/login/user_pod_row.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 is the stylesheet used by user pods row of account picker UI.
  */
 
 podrow {
   -webkit-box-align: center;
   -webkit-box-pack: center;
-  -webkit-transition: width 180ms ease;
+  /* Temporarily disabled because animation interferes with updating screen's
+   size. */
+  /* -webkit-transition: width 180ms ease; */
   display: -webkit-box;
   max-height: 650px;
-  overflow: hidden;
-  padding: 23px 15px;
-  position: relative;
+  overflow: visible;
+}
+
+podrow[ncolumns='4'] {
+  width: 880px;
+}
+
+podrow[ncolumns='5'] {
+  width: 1100px;
+}
+
+podrow[ncolumns='6'] {
   width: 1152px;
 }
 
-podrow[ncolumns='4'] {
-  width: 900px;
-}
-
 /* Hide the pod row while images are loading. */
 podrow.images-loading {
   visibility: hidden;
 }
 
 .pod {
   -webkit-transform: scale(0.9);
   -webkit-transition: all 180ms ease;
   background-color: white;
   border-radius: 2px;
@@ skipping 377 matching lines @@
 .pod.public-account.expanded .name,
 .pod.public-account.expanded .learn-more {
   display: none;
 }
 
 .pod.public-account.expanded .side-pane-divider,
 .pod.public-account.expanded .side-pane-container,
 .pod.public-account.animating .side-pane-container {
   visibility: visible;
 }