Hack to fix settings-checkbox mixin for 1.6.0

chrome/browser/resources/settings/controls/settings_checkbox.html

Index: chrome/browser/resources/settings/controls/settings_checkbox.html
diff --git a/chrome/browser/resources/settings/controls/settings_checkbox.html b/chrome/browser/resources/settings/controls/settings_checkbox.html
index fb3378372b15b3a3035818b292a2f50e1cc9976a..0acdf3da05e314fd7641dcb6186b9aac83099f6c 100644
--- a/chrome/browser/resources/settings/controls/settings_checkbox.html
+++ b/chrome/browser/resources/settings/controls/settings_checkbox.html
@@ -20,6 +20,13 @@
         @apply(--settings-secondary);
       }
 
+      #nonexistent {
+        /* HACK(michaelpg): Inform Polymer that this mixin can set "display". */
+        --settings-secondary-unchecked: {
+          display: block;
+        };
+      }
+
       paper-checkbox:not([checked]) .secondary {
         @apply(--settings-secondary-unchecked);
       }