arc: Use overlay to show links from ToS.

chrome/browser/resources/chromeos/arc_support/main.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. */
 
 html,
 body,
 webview,
 .section {
   font-family: 'Roboto';
   height: 100%;
@@ skipping 69 matching lines @@
   background-size: 16px;
 }
 
 .image-header {
   display: block;
   height: 300px;
   padding: 0;
   width: 960px;
 }
 
+.overlay-text .page {
+  width: 480px;
+}
+
+.overlay-text webview {
+  display: none;
+}
+
+.overlay-url .page {
+  width: 640px;
+}
+
+.overlay-url span {
+  display: none;
+}
+
+.overlay-url webview {
+  display: block;
+  height: 300px;
+  margin: 24px 8px 8px 8px;
+  padding: 0;
+  width: 100%;
+}
+
 .page {
   font-family: 'Roboto';
   font-size: 13px;
   text-align: left;
-  width: 480px;
 }
 
 .scrollable {
   flex: auto;
   margin: 0;
   overflow: auto;
   padding: 0;
 }
 
 .section {
@@ skipping 75 matching lines @@
 
 a:link {
   color: rgb(51, 103, 214);
   text-decoration: none;
 }
 
 a:visited {
   color: rgb(51, 103, 214);
   text-decoration: none;
 }