Have Node::document() return a reference instead of a pointer

Source/core/html/track/LoadableTextTrack.cpp

 /*
  * Copyright (C) 2011 Google 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 16 matching lines @@
 
 #include "core/html/track/LoadableTextTrack.h"
 
 #include "core/html/HTMLTrackElement.h"
 #include "core/html/track/TextTrackCueList.h"
 #include "core/html/track/TextTrackRegionList.h"
 
 namespace WebCore {
 
 LoadableTextTrack::LoadableTextTrack(HTMLTrackElement* track, const String& kind, const String& label, const String& language)
-    : TextTrack(track->document(), track, kind, label, language, TrackElement)
+    : TextTrack(&track->document(), track, kind, label, language, TrackElement)
     , m_trackElement(track)
     , m_loadTimer(this, &LoadableTextTrack::loadTimerFired)
     , m_isDefault(false)
 {
 }
 
 LoadableTextTrack::~LoadableTextTrack()
 {
 }
 
@@ skipping 34 matching lines @@
         m_loader->cancelLoad();
 
     if (!m_trackElement)
         return;
 
     // 4.8.10.12.3 Sourcing out-of-band text tracks (continued)
 
     // 4. Download: If URL is not the empty string, perform a potentially CORS-enabled fetch of URL, with the
     // mode being the state of the media element's crossorigin content attribute, the origin being the
     // origin of the media element's Document, and the default origin behaviour set to fail.
-    m_loader = TextTrackLoader::create(this, static_cast<ScriptExecutionContext*>(m_trackElement->document()));
+    m_loader = TextTrackLoader::create(this, static_cast<ScriptExecutionContext*>(&m_trackElement->document()));
     if (!m_loader->load(m_url, m_trackElement->mediaElementCrossOriginAttribute()))
         m_trackElement->didCompleteLoad(this, HTMLTrackElement::Failure);
 }
 
 void LoadableTextTrack::newCuesAvailable(TextTrackLoader* loader)
 {
     ASSERT_UNUSED(loader, m_loader == loader);
 
     Vector<RefPtr<TextTrackCue> > newCues;
     m_loader->getNewCues(newCues);
@@ skipping 53 matching lines @@
             return index;
         ++index;
     }
     ASSERT_NOT_REACHED();
 
     return 0;
 }
 
 } // namespace WebCore