Have Document::topDocument() return a reference

Source/core/dom/FullscreenElementStack.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, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 239 matching lines @@
         // 7. Optionally, display a message indicating how the user can exit displaying the context object fullscreen.
         return;
     } while (0);
 
     m_fullScreenErrorEventTargetQueue.append(element ? element : document()->documentElement());
     m_fullScreenChangeDelayTimer.startOneShot(0);
 }
 
 void FullscreenElementStack::webkitCancelFullScreen()
 {
-    ASSERT(document()->topDocument());
     // The Mozilla "cancelFullScreen()" API behaves like the W3C "fully exit fullscreen" behavior, which
     // is defined as:
     // "To fully exit fullscreen act as if the exitFullscreen() method was invoked on the top-level browsing
     // context's document and subsequently empty that document's fullscreen element stack."
-    if (!fullscreenElementFrom(*document()->topDocument()))
+    if (!fullscreenElementFrom(document()->topDocument()))
         return;
 
     // To achieve that aim, remove all the elements from the top document's stack except for the first before
     // calling webkitExitFullscreen():
     Vector<RefPtr<Element> > replacementFullscreenElementStack;
-    replacementFullscreenElementStack.append(fullscreenElementFrom(*document()->topDocument()));
-    FullscreenElementStack& topFullscreenElementStack = from(*document()->topDocument());
+    replacementFullscreenElementStack.append(fullscreenElementFrom(document()->topDocument()));
+    FullscreenElementStack& topFullscreenElementStack = from(document()->topDocument());
     topFullscreenElementStack.m_fullScreenElementStack.swap(replacementFullscreenElementStack);
     topFullscreenElementStack.webkitExitFullscreen();
 }
 
 void FullscreenElementStack::webkitExitFullscreen()
 {
     // The exitFullscreen() method must run these steps:
 
     // 1. Let doc be the context object. (i.e. "this")
     Document* currentDoc = document();
@@ skipping 155 matching lines @@
         m_fullScreenRenderer->unwrapRenderer();
 
     m_fullScreenElement = nullptr;
     document()->setNeedsStyleRecalc(SubtreeStyleChange);
 
     // When webkitCancelFullScreen is called, we call webkitExitFullScreen on the topDocument(). That
     // means that the events will be queued there. So if we have no events here, start the timer on
     // the exiting document.
     Document* exitingDocument = document();
     if (m_fullScreenChangeEventTargetQueue.isEmpty() && m_fullScreenErrorEventTargetQueue.isEmpty())
-        exitingDocument = document()->topDocument();
+        exitingDocument = &document()->topDocument();
     ASSERT(exitingDocument);
     from(*exitingDocument).m_fullScreenChangeDelayTimer.startOneShot(0);
 }
 
 void FullscreenElementStack::setFullScreenRenderer(RenderFullScreen* renderer)
 {
     if (renderer == m_fullScreenRenderer)
         return;
 
     if (renderer && m_savedPlaceholderRenderStyle) {
@@ skipping 112 matching lines @@
         if (!target)
             target = fullscreen->webkitCurrentFullScreenElement();
     }
 
     if (!target)
         target = doc;
     m_fullScreenChangeEventTargetQueue.append(target);
 }
 
 } // namespace WebCore