Hide the default checkbox on Safe Browsing interstitials

For some reason, the default checkbox appears underneath the styled checkbox on Mac. This sets the visibility to hidden so that it won't peek out anymore.

BUG=386867
R=dbeam@chromium.org

Review URL: https://codereview.chromium.org/378093003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@281974 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/ssl/interstitial_v2.css

@@ -90,6 +90,10 @@ h2 {
   width: 72px;
 }
 
+input[type=checkbox] {
+  visibility: hidden;
+}
+
 .interstitial-wrapper {
   box-sizing: border-box;
   font-size: 1em;