arc: avoid checkbox AutomationNode issue

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 24 matching lines @@
 }
 
 #terms-view {
   width: 640px;
 }
 
 .button-separator {
   width: 1px;
 }
 
-.checkbox-container {
-  margin: 0;
-  padding: 0 8px 0 0;
-}
-
 .checkbox-option {
   height: 12px;
   margin: 0;
   padding: 0;
   width: 12px;
 }
 
 .checkbox-text {
   color: rgba(0, 0, 0, 0.54);
   font-size: 10px;
@@ skipping 41 matching lines @@
   flex-direction: column;
 }
 
 .section-checkbox-container {
   margin: auto;
   padding: 8px 0 0 0;
   text-align: left;
   width: 640px;
 }
 
+.section-checkbox-container > input[type='checkbox'] {
+  flex-shrink: 0;
+  margin: 0 8px 0 0;
+}
+
 .section-terms {
   border: 1px solid #e6e6e6;
   color: rgba(0, 0, 0, 0.54);
   flex: auto;
   margin: 0 auto 8px auto;
   overflow: hidden;
   padding: 0;
   width: 640px;
 }
 
@@ skipping 37 matching lines @@
 
 a:link {
   color: rgb(51, 103, 214);
   text-decoration: none;
 }
 
 a:visited {
   color: rgb(51, 103, 214);
   text-decoration: none;
 }