Remove HTMLSourceElement media listener if media attribute is empty

third_party/WebKit/Source/core/html/HTMLSourceElement.cpp

 /*
  * Copyright (C) 2007, 2008, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 63 matching lines @@
 }
 
 DEFINE_NODE_FACTORY(HTMLSourceElement)
 
 HTMLSourceElement::~HTMLSourceElement()
 {
 }
 
 void HTMLSourceElement::createMediaQueryList(const AtomicString& media)
 {
+    removeMediaQueryListListener();
     if (media.isEmpty())
         return;
 
-    removeMediaQueryListListener();
     MediaQuerySet* set = MediaQuerySet::create(media);
     m_mediaQueryList = MediaQueryList::create(&document(), &document().mediaQueryMatcher(), set);

[cbiesinger, 2016/09/07 16:01:41]

Should this also be set to null if media.isEmpty()?

     addMediaQueryListListener();
 }
 
 void HTMLSourceElement::didMoveToNewDocument(Document& oldDocument)
 {
     createMediaQueryList(fastGetAttribute(mediaAttr));
     HTMLElement::didMoveToNewDocument(oldDocument);
 }
 
 Node::InsertionNotificationRequest HTMLSourceElement::insertedInto(ContainerNode* insertionPoint)
@@ skipping 100 matching lines @@
 }
 
 DEFINE_TRACE(HTMLSourceElement)
 {
     visitor->trace(m_mediaQueryList);
     visitor->trace(m_listener);
     HTMLElement::trace(visitor);
 }
 
 } // namespace blink