Have Document::timeline() / Document::transitionTimeline() return a reference

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 529 matching lines @@
         clearAXObjectCache();
 
     if (m_styleSheetList)
         m_styleSheetList->detachFromDocument();
 
     if (m_import) {
         m_import->wasDetachedFromDocument();
         m_import = 0;
     }
 
-    if (m_timeline) {
-        m_timeline->detachFromDocument();
-    }
-
-    if (m_transitionTimeline) {
-        m_transitionTimeline->detachFromDocument();
-    }
+    m_timeline->detachFromDocument();
+    m_transitionTimeline->detachFromDocument();
 
     m_styleEngine.clear(); // We need to destory CSSFontSelector before destroying m_fetcher.
 
     if (m_elemSheet)
         m_elemSheet->clearOwnerNode();
 
     // It's possible for multiple Documents to end up referencing the same ResourceFetcher (e.g., SVGImages
     // load the initial empty document and the SVGDocument with the same DocumentLoader).
     if (m_fetcher->document() == this)
         m_fetcher->setDocument(0);
@@ skipping 4871 matching lines @@
 void Document::defaultEventHandler(Event* event)
 {
     if (frame() && frame()->remotePlatformLayer()) {
         frame()->chromeClient().forwardInputEvent(this, event);
         return;
     }
     Node::defaultEventHandler(event);
 }
 
 } // namespace WebCore