Use NodeAsRangeFirstNode() as Range::FirstNode() again.

third_party/WebKit/Source/core/dom/Range.cpp

 /*
  * (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, 2010, 2011 Apple Inc. All
  * rights reserved.
  * Copyright (C) 2011 Motorola Mobility. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 1415 matching lines @@
   for (Node* n = FirstNode(); n != past_last; n = NodeTraversal::Next(*n)) {
     if (n->IsDocumentTypeNode()) {
       exception_state.ThrowDOMException(kHierarchyRequestError,
                                         "The Range contains a doctype node.");
       return;
     }
   }
 }
 
 Node* Range::FirstNode() const {
-  if (start_.Container().IsCharacterDataNode())
-    return &start_.Container();
-  if (Node* child = NodeTraversal::ChildAt(start_.Container(), start_.Offset()))
-    return child;
-  if (!start_.Offset())
-    return &start_.Container();
-  return NodeTraversal::NextSkippingChildren(start_.Container());
+  return StartPosition().ToOffsetInAnchor().NodeAsRangeFirstNode();

[yosin_UTC9, 2017/04/13 05:45:45]

We don't need to use |ToOffsetInAnchor()| here.
|Position::NodeAsRangeFirstNode()| does so.
BTW, we would like to call |ToOffsetInAnchor()| in
|Position::NodeAsRangeFirstNode()|.

[yoichio, 2017/04/13 06:04:39]

Done.

 }
 
 Node* Range::PastLastNode() const {
-  if (end_.Container().IsCharacterDataNode())
-    return NodeTraversal::NextSkippingChildren(end_.Container());
-  if (Node* child = NodeTraversal::ChildAt(end_.Container(), end_.Offset()))
-    return child;
-  return NodeTraversal::NextSkippingChildren(end_.Container());
+  return EndPosition().ToOffsetInAnchor().NodeAsRangePastLastNode();

[yosin_UTC9, 2017/04/13 05:45:45]

We don't need to use |ToOffsetInAnchor()| here.
|Position::NodeAsRangePastLastNode()| does so.
BTW, we would like to call |ToOffsetInAnchor()| in
|Position::NodeAsRangePastLastNode()|.

[yoichio, 2017/04/13 06:04:39]

Done.

 }
 
 IntRect Range::BoundingBox() const {
   IntRect result;
   Vector<IntRect> rects;
   TextRects(rects);
   for (const IntRect& rect : rects)
     result.Unite(rect);
   return result;
 }
@@ skipping 367 matching lines @@
                      .Data()
               << "start offset: " << range->startOffset()
               << ", end offset: " << range->endOffset();
   } else {
     LOG(INFO) << "Cannot show tree if range is null, or if boundary points are "
                  "invalid.";
   }
 }
 
 #endif