Don't mutate the DOM from inside an Element's constructor

Source/core/html/HTMLAudioElement.cpp

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 #include "config.h"
 #include "core/html/HTMLAudioElement.h"
 
 #include "HTMLNames.h"
+#include "core/dom/shadow/ShadowRoot.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 HTMLAudioElement::HTMLAudioElement(Document& document)
     : HTMLMediaElement(audioTag, document)
 {
     ScriptWrappable::init(this);
 }
 
 PassRefPtrWillBeRawPtr<HTMLAudioElement> HTMLAudioElement::create(Document& document)
 {
-    RefPtrWillBeRawPtr<HTMLAudioElement> audioElement(adoptRefWillBeRefCountedGarbageCollected(new HTMLAudioElement(document)));
-    audioElement->suspendIfNeeded();
-    return audioElement.release();
+    RefPtrWillBeRawPtr<HTMLAudioElement> audio = adoptRefWillBeRefCountedGarbageCollected(new HTMLAudioElement(document));
+    audio->ensureUserAgentShadowRoot();
+    audio->suspendIfNeeded();
+    return audio.release();
 }
 
 PassRefPtrWillBeRawPtr<HTMLAudioElement> HTMLAudioElement::createForJSConstructor(Document& document, const AtomicString& src)
 {
     RefPtrWillBeRawPtr<HTMLAudioElement> audio = adoptRefWillBeRefCountedGarbageCollected(new HTMLAudioElement(document));
+    audio->ensureUserAgentShadowRoot();
     audio->setPreload(AtomicString("auto", AtomicString::ConstructFromLiteral));
     if (!src.isNull())
         audio->setSrc(src);
     audio->suspendIfNeeded();
     return audio.release();
 }
 
 }