Have Document::topDocument() 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 2175 matching lines @@
     m_axObjectCache.clear();
 }
 
 AXObjectCache* Document::existingAXObjectCache() const
 {
     if (!AXObjectCache::accessibilityEnabled())
         return 0;
 
     // If the renderer is gone then we are in the process of destruction.
     // This method will be called before m_frame = 0.
-    if (!topDocument()->renderView())
+    if (!topDocument().renderView())
         return 0;
 
-    return topDocument()->m_axObjectCache.get();
+    return topDocument().m_axObjectCache.get();
 }
 
 AXObjectCache* Document::axObjectCache() const
 {
     if (!AXObjectCache::accessibilityEnabled())
         return 0;
 
     // The only document that actually has a AXObjectCache is the top-level
     // document.  This is because we need to be able to get from any WebCoreAXObject
     // to any other WebCoreAXObject on the same page.  Using a single cache allows
     // lookups across nested webareas (i.e. multiple documents).
-    Document* topDocument = this->topDocument();
+    Document& topDocument = this->topDocument();
 
     // If the document has already been detached, do not make a new axObjectCache.
-    if (!topDocument->renderView())
+    if (!topDocument.renderView())
         return 0;
 
     ASSERT(topDocument == this || !m_axObjectCache);
-    if (!topDocument->m_axObjectCache)
-        topDocument->m_axObjectCache = adoptPtr(new AXObjectCache(topDocument));
-    return topDocument->m_axObjectCache.get();
+    if (!topDocument.m_axObjectCache)
+        topDocument.m_axObjectCache = adoptPtr(new AXObjectCache(topDocument));
+    return topDocument.m_axObjectCache.get();
 }
 
 PassRefPtr<DocumentParser> Document::createParser()
 {
     if (isHTMLDocument()) {
         bool reportErrors = InspectorInstrumentation::collectingHTMLParseErrors(page());
         return HTMLDocumentParser::create(toHTMLDocument(this), reportErrors);
     }
     // FIXME: this should probably pass the frame instead
     return XMLDocumentParser::create(this, view());
@@ skipping 1704 matching lines @@
     // FIXME: If this document came from the file system, the HTML5
     // specificiation tells us to read the last modification date from the file
     // system.
     if (!foundDate)
         date.setMillisecondsSinceEpochForDateTime(currentTimeMS());
     return String::format("%02d/%02d/%04d %02d:%02d:%02d", date.month() + 1, date.monthDay(), date.fullYear(), date.hour(), date.minute(), date.second());
 }
 
 const KURL& Document::firstPartyForCookies() const
 {
-    return topDocument()->url();
+    return topDocument().url();
 }
 
 static bool isValidNameNonASCII(const LChar* characters, unsigned length)
 {
     if (!isValidNameStart(characters[0]))
         return false;
 
     for (unsigned i = 1; i < length; ++i) {
         if (!isValidNamePart(characters[i]))
             return false;
@@ skipping 347 matching lines @@
 Document* Document::parentDocument() const
 {
     if (!m_frame)
         return 0;
     LocalFrame* parent = m_frame->tree().parent();
     if (!parent)
         return 0;
     return parent->document();
 }
 
-Document* Document::topDocument() const
+Document& Document::topDocument() const
 {
     Document* doc = const_cast<Document*>(this);
     Element* element;
     while ((element = doc->ownerElement()))
         doc = &element->document();
 
-    return doc;
+    ASSERT(doc);
+    return *doc;
 }
 
 WeakPtr<Document> Document::contextDocument()
 {
     if (m_contextDocument)
         return m_contextDocument;
     if (m_frame)
         return m_weakFactory.createWeakPtr();
     return WeakPtr<Document>(nullptr);
 }
@@ skipping 1107 matching lines @@
 void Document::defaultEventHandler(Event* event)
 {
     if (frame() && frame()->remotePlatformLayer()) {
         frame()->chromeClient().forwardInputEvent(this, event);
         return;
     }
     Node::defaultEventHandler(event);
 }
 
 } // namespace WebCore