UA shadow root of <marquee> should not be exposed to user scripts

Source/core/html/HTMLMarqueeElement.js

Index: Source/core/html/HTMLMarqueeElement.js
diff --git a/Source/core/html/HTMLMarqueeElement.js b/Source/core/html/HTMLMarqueeElement.js
index 95ce320951fa2314b8c039052a23b21794ff2d97..b28c39346ab1dc1548f3965b5f68a39bd487cab8 100644
--- a/Source/core/html/HTMLMarqueeElement.js
+++ b/Source/core/html/HTMLMarqueeElement.js
@@ -91,7 +91,7 @@ installClass('HTMLMarqueeElement', function(HTMLMarqueeElementPrototype) {
     reflectBooleanAttribute(HTMLMarqueeElementPrototype, 'truespeed', 'trueSpeed');
 
     HTMLMarqueeElementPrototype.createdCallback = function() {
-        var shadow = this.createShadowRoot();
+        var shadow = this.createUserAgentShadowRoot();
         var style = document.createElement('style');
         style.textContent = ':host { display: inline-block; width: -webkit-fill-available; overflow: hidden; text-align: initial; }'
             + ':host([direction="up"]), :host([direction="down"]) { overflow: initial; overflow-y: hidden; }';