Correcting issues noted in a11y review for Desktop FRE.

chrome/browser/resources/welcome/welcome.css

 /* Copyright 2016 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 {
   align-items: center;
   color: var(--paper-grey-900);
   display: flex;
   flex-direction: column;
   font-size: 100%;
@@ skipping 100 matching lines @@
 .heading {
   animation: fadeInAndSlideUp 600ms 1.9s cubic-bezier(.4, .2, 0, 1) both;
   font-size: 2.125em;
   margin-bottom: .25em;
   margin-top: 1.5em;
   text-align: center;
 }
 
 .subheading {
   animation: fadeInAndSlideUp 600ms 1.9s cubic-bezier(.4, .2, 0, 1) both;
-  color: var(--google-grey-500);
+  color: #939393;
   font-size: 1em;
+  font-weight: 500;
   margin-top: .25em;
   text-align: center;
 }
 
 .logo {
   animation: fadeIn 600ms both, bounce 1s 600ms linear both;
   height: 96px;
   position: relative;
   width: 96px;
 }
 
 .logo-icon {
   animation: spin 2.4s cubic-bezier(.4, .2, 0, 1) both,
              colorize 300ms 700ms linear both;
-  content: -webkit-image-set(url(chrome://welcome/logo.png) 1x,
-                             url(chrome://welcome/logo2x.png) 2x);
+  background-image: -webkit-image-set(url(chrome://welcome/logo.png) 1x,
+                                      url(chrome://welcome/logo2x.png) 2x);
+  background-size: 100%;
   height: 96px;
-  left: 0;
-  position: absolute;
   width: 96px;
 }
 
 .logo-shadow {
   -webkit-filter: blur(16px);
   animation: fadeInAndSlideDownShadow 300ms 600ms both;
   background: rgba(0, 0, 0, .2);
   border-radius: 50%;
   height: 96px;
   position: absolute;
@@ skipping 58 matching lines @@
   height: 24px;
   position: absolute;
   width: 74px;
 }
 
 @media(max-height: 608px) {
   .watermark {
     display: none;
   }
 }