Utilize Position::IsEquivalent() in {Up,Down}streamIgnoringEditingBoundaries()

third_party/WebKit/Source/core/editing/Position.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2009 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 337 matching lines @@
 
 template <typename Strategy>
 bool PositionTemplate<Strategy>::operator>=(
     const PositionTemplate<Strategy>& other) const {
   return ComparePositions(*this, other) >= 0;
 }
 
 template <typename Strategy>
 bool PositionTemplate<Strategy>::IsEquivalent(
     const PositionTemplate<Strategy>& other) const {
+  if (IsNull())

[Xiaocheng, 2017/05/12 18:00:05]

This should go to the previous patch.

[yoichio, 2017/05/15 01:41:53]

I oppose this change from the math sense.
For example, Nan should not equal any number including
 Nan itself.
How about |while(position.IsValid() && position != lastposition)|
  in the caller? 

[yosin_UTC9, 2017/05/15 05:12:57]

Oops, I missed rebasing.
Talked offline.

In this patch, we use Position::IsEqualivalent() as replacement of operator==()
to
minimize patch size.

We'll get rid of null-Position usage in future.

+    return other.IsNull();
   if (anchor_type_ == other.anchor_type_)
     return *this == other;
   return ToOffsetInAnchor() == other.ToOffsetInAnchor();
 }
 
 template <typename Strategy>
 bool PositionTemplate<Strategy>::AtFirstEditingPositionForNode() const {
   if (IsNull())
     return true;
   // FIXME: Position before anchor shouldn't be considered as at the first
@@ skipping 334 matching lines @@
 }
 
 void showTree(const blink::Position* pos) {
   if (pos)
     pos->ShowTreeForThis();
   else
     LOG(INFO) << "Cannot showTree for <null>";
 }
 
 #endif