Have Range constructor take a Document reference in argument

Source/core/dom/Range.h

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Gunnstein Lye (gunnstein@netcom.no)
  * (C) 2000 Frederik Holljen (frederik.holljen@hig.no)
  * (C) 2001 Peter Kelly (pmk@post.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 31 matching lines @@
 class Document;
 class DocumentFragment;
 class ExceptionState;
 class FloatQuad;
 class Node;
 class NodeWithIndex;
 class Text;
 
 class Range : public RefCounted<Range>, public ScriptWrappable {
 public:
-    static PassRefPtr<Range> create(Document*);
-    static PassRefPtr<Range> create(Document*, Node* startContainer, int startOffset, Node* endContainer, int endOffset);
-    static PassRefPtr<Range> create(Document*, const Position&, const Position&);
+    static PassRefPtr<Range> create(Document&);
+    static PassRefPtr<Range> create(Document&, Node* startContainer, int startOffset, Node* endContainer, int endOffset);
+    static PassRefPtr<Range> create(Document&, const Position&, const Position&);
     ~Range();
 
-    Document* ownerDocument() const { return m_ownerDocument.get(); }
+    Document& ownerDocument() const { ASSERT(m_ownerDocument); return *m_ownerDocument.get(); }
     Node* startContainer() const { return m_start.container(); }
     int startOffset() const { return m_start.offset(); }
     Node* endContainer() const { return m_end.container(); }
     int endOffset() const { return m_end.offset(); }
 
     Node* startContainer(ExceptionState&) const;
     int startOffset(ExceptionState&) const;
     Node* endContainer(ExceptionState&) const;
     int endOffset(ExceptionState&) const;
     bool collapsed(ExceptionState&) const;
@@ skipping 75 matching lines @@
     void expand(const String&, ExceptionState&);
 
     PassRefPtr<ClientRectList> getClientRects() const;
     PassRefPtr<ClientRect> getBoundingClientRect() const;
 
 #ifndef NDEBUG
     void formatForDebugger(char* buffer, unsigned length) const;
 #endif
 
 private:
-    explicit Range(Document*);
-    Range(Document*, Node* startContainer, int startOffset, Node* endContainer, int endOffset);
+    explicit Range(Document&);
+    Range(Document&, Node* startContainer, int startOffset, Node* endContainer, int endOffset);
 
-    void setDocument(Document*);
+    void setDocument(Document&);
 
     Node* checkNodeWOffset(Node*, int offset, ExceptionState&) const;
     void checkNodeBA(Node*, ExceptionState&, const char* methodName) const;
     void checkDeleteExtract(ExceptionState&);
     int maxStartOffset() const;
     int maxEndOffset() const;
 
     enum ActionType { DELETE_CONTENTS, EXTRACT_CONTENTS, CLONE_CONTENTS };
     PassRefPtr<DocumentFragment> processContents(ActionType, ExceptionState&);
     static PassRefPtr<Node> processContentsBetweenOffsets(ActionType, PassRefPtr<DocumentFragment>, Node*, unsigned startOffset, unsigned endOffset, ExceptionState&);
     static void processNodes(ActionType, Vector<RefPtr<Node> >&, PassRefPtr<Node> oldContainer, PassRefPtr<Node> newContainer, ExceptionState&);
     enum ContentsProcessDirection { ProcessContentsForward, ProcessContentsBackward };
     static PassRefPtr<Node> processAncestorsAndTheirSiblings(ActionType, Node* container, ContentsProcessDirection, PassRefPtr<Node> clonedContainer, Node* commonRoot, ExceptionState&);
 
-    RefPtr<Document> m_ownerDocument;
+    RefPtr<Document> m_ownerDocument; // Cannot be null.

[do-not-use, 2013/09/03 15:43:22]

BTW, a Reference-flavoured smart pointer class would be really useful here. It
would take care of ref'ing / unref'ing, while making it obvious that the value
cannot be NULL.

The code would look like:
Ref<Document> m_ownerDocument;
m_document.get() would return a (const) reference.
Such code would not compile: if (m_ownerDocument) { ... }

WebKit has recently added such class in WTF:
https://bugs.webkit.org/show_bug.cgi?id=120570

I would propose to port that WebKit patch in a follow-up to improve this. Please
let me know if you agree.

     RangeBoundaryPoint m_start;
     RangeBoundaryPoint m_end;
 };
 
 PassRefPtr<Range> rangeOfContents(Node*);
 
 bool areRangesEqual(const Range*, const Range*);
 
 } // namespace
 
 #ifndef NDEBUG
 // Outside the WebCore namespace for ease of invocation from gdb.
 void showTree(const WebCore::Range*);
 #endif
 
 #endif