Remove details strings used by iframes on network error pages

components/neterror/resources/neterror.css

Index: components/neterror/resources/neterror.css
diff --git a/components/neterror/resources/neterror.css b/components/neterror/resources/neterror.css
index 071061411e36ebac9bd497be90c2533722565ec8..1cbc66cf336f9c49151a349c886e1a7b103f6ce5 100644
--- a/components/neterror/resources/neterror.css
+++ b/components/neterror/resources/neterror.css
@@ -268,6 +268,7 @@ html[subframe] body {
   -webkit-justify-content: center;
   left: 0;
   position: absolute;
+  text-align: center;
   top: 0;
   transition: background-color .2s ease-in-out;
   width: 100%;
@@ -352,6 +353,10 @@ html[subframe] body {
   will-change: -webkit-filter, background-color;
 }
 
+.offline #main-message > p {
+  display: none;
+}
+
 .offline.inverted {
   -webkit-filter: invert(100%);
   background-color: #000;