WebUI: Fix radio and checkbox behavior when text selected.

ui/webui/resources/css/widgets.css

Index: ui/webui/resources/css/widgets.css
diff --git a/ui/webui/resources/css/widgets.css b/ui/webui/resources/css/widgets.css
index 2ab881aa5e286c7a88fc6e040f3c6a9b4230866a..1ad78ba542583dc4bf7f1a9598fe2b0f4833d97a 100644
--- a/ui/webui/resources/css/widgets.css
+++ b/ui/webui/resources/css/widgets.css
@@ -284,6 +284,7 @@ input:disabled:-webkit-any([type='password'],
  */
 
 :-webkit-any(.checkbox, .radio) label {
+  -webkit-user-select: none;
   /* Don't expand horizontally: <http://crbug.com/112091>. */
   align-items: center;
   display: inline-flex;
@@ -297,7 +298,6 @@ input:disabled:-webkit-any([type='password'],
 
 :-webkit-any(.checkbox, .radio) label input ~ span {
   -webkit-margin-start: 0.6em;
-  -webkit-user-select: none;
   /* Make sure long spans wrap at the same horizontal position they start. */
   display: block;
 }
@@ -314,4 +314,4 @@ extensionview {
   display: inline-block;
   height: 300px;
   width: 300px;
-}
+}