Convert an assertion to if-condition in ReplaceSelectionCommand::doApply()

third_party/WebKit/Source/core/editing/commands/ReplaceSelectionCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010, 2011 Google 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
@@ skipping 1130 matching lines @@
     HTMLBRElement* endBR = isHTMLBRElement(*mostForwardCaretPosition(insertionPos).anchorNode()) ? toHTMLBRElement(mostForwardCaretPosition(insertionPos).anchorNode()) : 0;
     VisiblePosition originalVisPosBeforeEndBR;
     if (endBR)
         originalVisPosBeforeEndBR = previousPositionOf(VisiblePosition::beforeNode(endBR));
 
     Element* enclosingBlockOfInsertionPos = enclosingBlock(insertionPos.anchorNode());
 
     // Adjust insertionPos to prevent nesting.
     // If the start was in a Mail blockquote, we will have already handled adjusting insertionPos above.
     if (m_preventNesting && enclosingBlockOfInsertionPos && !isTableCell(enclosingBlockOfInsertionPos) && !startIsInsideMailBlockquote) {
-        DCHECK_NE(enclosingBlockOfInsertionPos, currentRoot);

[Xiaocheng, 2016/09/12 04:58:56]

What's the reason the assertion was introduced? Is there any buggy behavior that
it's trying to detect?

[yosin_UTC9, 2016/09/12 05:21:38]

This assertion is introduced by https://bugs.webkit.org/show_bug.cgi?id=8592
It seems this assertion is correct, we should not adjust
|enclosingBlockOfInsertionPos| when |enclosingBlockOfInsertionPos ==
currentRoot|.

         VisiblePosition visibleInsertionPos = createVisiblePosition(insertionPos);
         if (isEndOfBlock(visibleInsertionPos) && !(isStartOfBlock(visibleInsertionPos) && fragment.hasInterchangeNewlineAtEnd()))
             insertionPos = Position::inParentAfterNode(*enclosingBlockOfInsertionPos);
         else if (isStartOfBlock(visibleInsertionPos))
             insertionPos = Position::inParentBeforeNode(*enclosingBlockOfInsertionPos);
     }
 
     // Paste at start or end of link goes outside of link.
     insertionPos = positionAvoidingSpecialElementBoundary(insertionPos, editingState);
     if (editingState->isAborted())
@@ skipping 596 matching lines @@
     visitor->trace(m_startOfInsertedContent);
     visitor->trace(m_endOfInsertedContent);
     visitor->trace(m_insertionStyle);
     visitor->trace(m_documentFragment);
     visitor->trace(m_startOfInsertedRange);
     visitor->trace(m_endOfInsertedRange);
     CompositeEditCommand::trace(visitor);
 }
 
 } // namespace blink