Introduce {next,previous}PositionOf() as replacement of {next,previous}() member functions in Positi

Source/core/editing/commands/BreakBlockquoteCommand.cpp

 /*
  * Copyright (C) 2005 Apple Computer, 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 108 matching lines @@
 
     // If we're inserting the break at the end of the quoted content, we don't need to break the quote.
     if (isLastVisPosInNode) {
         setEndingSelection(VisibleSelection(positionBeforeNode(breakElement.get()), TextAffinity::Downstream, endingSelection().isDirectional()));
         rebalanceWhitespace();
         return;
     }
 
     // Don't move a line break just after the caret.  Doing so would create an extra, empty paragraph
     // in the new blockquote.
-    if (lineBreakExistsAtVisiblePosition(visiblePos))
-        pos = pos.next();
+    if (lineBreakExistsAtVisiblePosition(visiblePos)) {
+        // TODO(yosin) We should use |PositionMoveType::Character| for
+        // |nextPositionOf()| to avoid editing middle of character.
+        pos = nextPositionOf(pos, PositionMoveType::CodePoint);
+    }
 
     // Adjust the position so we don't split at the beginning of a quote.
-    while (isFirstVisiblePositionInNode(VisiblePosition(pos), toHTMLQuoteElement(enclosingNodeOfType(pos, isMailHTMLBlockquoteElement))))
-        pos = pos.previous();
+    while (isFirstVisiblePositionInNode(VisiblePosition(pos), toHTMLQuoteElement(enclosingNodeOfType(pos, isMailHTMLBlockquoteElement)))) {
+        // TODO(yosin) We should use |PositionMoveType::Character| for
+        // |previousPositionOf()| to avoid editing middle character.
+        pos = previousPositionOf(pos, PositionMoveType::CodePoint);
+    }
 
     // startNode is the first node that we need to move to the new blockquote.
     Node* startNode = pos.anchorNode();
     ASSERT(startNode);
 
     // Split at pos if in the middle of a text node.
     if (startNode->isTextNode()) {
         Text* textNode = toText(startNode);
         int textOffset = pos.computeOffsetInContainerNode();
         if ((unsigned)textOffset >= textNode->length()) {
@@ skipping 67 matching lines @@
 
     // Make sure the cloned block quote renders.
     addBlockPlaceholderIfNeeded(clonedBlockquote.get());
 
     // Put the selection right before the break.
     setEndingSelection(VisibleSelection(positionBeforeNode(breakElement.get()), TextAffinity::Downstream, endingSelection().isDirectional()));
     rebalanceWhitespace();
 }
 
 } // namespace blink