Issue 6441 - Avoid unnecessary shadow root

include.preload.js

Index: include.preload.js
===================================================================
--- a/include.preload.js
+++ b/include.preload.js
@@ -359,27 +359,33 @@
   {
     // Use Shadow DOM if available as to not mess with with web pages that
     // rely on the order of their own <style> tags (#309). However, creating
     // a shadow root breaks running CSS transitions. So we have to create
     // the shadow root before transistions might start (#452).
     if (!("createShadowRoot" in document.documentElement))
       return null;
 
+    // Both Firefox and Chrome 66+ support user style sheets, so we can avoid
+    // creating an unnecessary shadow root on these platforms.
+    let [, version] = /\bChrome\/(\d+)\.\d+/.exec(navigator.userAgent) || [];
+    if (isNaN(version) || version >= 66)
+      return null;

[Sebastian Noack, 2018/03/09 00:28:13]

I think this can be somewhat simplified:

  let match = /\bChrome\/(\d+)/.exec(navigator.userAgent);
  if (!match || match[1] >= 66)
    return null;

Also note that I didn't care to check whether there is a minor version number.

[Manish Jethani, 2018/03/09 00:33:29]

Done.

+
     // Using shadow DOM causes issues on some Google websites,
     // including Google Docs, Gmail and Blogger (#1770, #2602, #2687).
     if (/\.(?:google|blogger)\.com$/.test(document.domain))
       return null;
 
     // Finally since some users have both AdBlock and Adblock Plus installed we
     // have to consider how the two extensions interact. For example we want to
     // avoid creating the shadowRoot twice.
     let shadow = document.documentElement.shadowRoot ||
                  document.documentElement.createShadowRoot();
-    shadow.appendChild(document.createElement("shadow"));
+    shadow.appendChild(document.createElement("content"));
 
     return shadow;
   },
 
   addSelectorsInline(selectors, groupName)
   {
     let style = this.styles.get(groupName);