CrOs first-run UI polished.

chrome/browser/resources/chromeos/first_run/app/style.css

 /**
  * Copyright 2013 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 {
   margin: 0;
   padding: 0;
 }
 
 .step.dialog {
   align-items: center;
   display: flex;
   flex-direction: column;
-  height: 475px;
   padding: 40px;
   text-align: center;
   width: 720px;
 }
 
 .step.dialog h1 {
   font-size: 30px;
   margin-bottom: 16px;
   margin-top: 0;
 }
 
 .step.dialog p {
   font-size: 15px;
   margin-bottom: 0;
+  margin-top: 0;
 }
 
 .step.dialog .controls {
-  display: flex;
-  flex-direction: column;
-  flex-grow: 1;
-}
-
-.step.dialog .controls .margin-top {
-  flex-grow: 8;
-}
-
-.step.dialog .controls .margin-bottom {
-  flex-grow: 5;
+  margin-bottom: 0;
+  margin-top: 40px;
 }
 
 .step.dialog .controls button {
   font-size: 12px;
   min-width: 0;
   padding: 0 35px;
   text-shadow: 0 1px 0 rgba(0, 0, 0, 0.3);
 }
 
 .step.dialog .window-header {
@@ skipping 14 matching lines @@
   -webkit-padding-end: 10px;
   display: flex;
   justify-content: flex-end;
 }
 
 .step.dialog .topbutton-bar button {
   -webkit-app-region: no-drag;
   -webkit-margin-end: 0;
   display: inline;
 }
+
+.step.dialog .greeting-image {
+  margin-bottom: 49px;
+  margin-top: 64px;
+}