Introduce few const getters for dom classes

third_party/WebKit/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 664 matching lines @@
     styleEngine().clearResolver();
 }
 
 DOMImplementation& Document::implementation()
 {
     if (!m_implementation)
         m_implementation = DOMImplementation::create(*this);
     return *m_implementation;
 }
 
+DOMImplementation* Document::maybeImplementation() const
+{
+    return m_implementation.get();
+}
+
 bool Document::hasAppCacheManifest() const
 {
     return isHTMLHtmlElement(documentElement()) && documentElement()->hasAttribute(manifestAttr);
 }
 
 Location* Document::location() const
 {
     if (!frame())
         return 0;
 
@@ skipping 2750 matching lines @@
     return true;
 }
 
 StyleSheetList* Document::styleSheets()
 {
     if (!m_styleSheetList)
         m_styleSheetList = StyleSheetList::create(this);
     return m_styleSheetList.get();
 }
 
+StyleSheetList* Document::maybeStyleSheets() const
+{
+    return m_styleSheetList;
+}
+
 String Document::preferredStylesheetSet() const
 {
     return m_styleEngine->preferredStylesheetSetName();
 }
 
 String Document::selectedStylesheetSet() const
 {
     return m_styleEngine->selectedStylesheetSetName();
 }
 
@@ skipping 2564 matching lines @@
 #ifndef NDEBUG
 using namespace blink;
 void showLiveDocumentInstances()
 {
     Document::WeakDocumentSet& set = Document::liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (Document* document : set)
         fprintf(stderr, "- Document %p URL: %s\n", document, document->url().getString().utf8().data());
 }
 #endif