Introduce Position::IsEquivalent()

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 335 matching lines @@
   return ComparePositions(*this, other) > 0;
 }
 
 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())
+    return other.IsNull();

[yoichio, 2017/05/15 01:43:05]

nlgtm because Nan != Nan generally.

[yosin_UTC9, 2017/05/15 04:08:15]

IsNull() doesn't mean NaN.
Also, Position::operator==() does same thing about IsNull()

template <typename Strategy>
bool operator==(const PositionTemplate<Strategy>& a,
                const PositionTemplate<Strategy>& b) {
  if (a.IsNull())
    return b.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
   // editing position for node since that position resides outside of the node.
   switch (anchor_type_) {
     case PositionAnchorType::kOffsetInAnchor:
       return offset_ == 0;
     case PositionAnchorType::kBeforeChildren:
     case PositionAnchorType::kBeforeAnchor:
@@ skipping 328 matching lines @@
 }
 
 void showTree(const blink::Position* pos) {
   if (pos)
     pos->ShowTreeForThis();
   else
     LOG(INFO) << "Cannot showTree for <null>";
 }
 
 #endif