Ensure valid VisiblePosition input for character{Before,After}

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 1451 matching lines @@
     return true;
 }
 
 static bool isCharacterSmartReplaceExemptConsideringNonBreakingSpace(UChar32 character, bool previousCharacter)
 {
     return isCharacterSmartReplaceExempt(character == noBreakSpaceCharacter ? ' ' : character, previousCharacter);
 }
 
 void ReplaceSelectionCommand::addSpacesForSmartReplace(EditingState* editingState)
 {
-    VisiblePosition startOfInsertedContent = positionAtStartOfInsertedContent();
     VisiblePosition endOfInsertedContent = positionAtEndOfInsertedContent();
-
     Position endUpstream = mostBackwardCaretPosition(endOfInsertedContent.deepEquivalent());
     Node* endNode = endUpstream.computeNodeBeforePosition();
     int endOffset = endNode && endNode->isTextNode() ? toText(endNode)->length() : 0;
     if (endUpstream.isOffsetInAnchor()) {
         endNode = endUpstream.computeContainerNode();
         endOffset = endUpstream.offsetInContainerNode();
     }
 
     bool needsTrailingSpace = !isEndOfParagraphDeprecated(endOfInsertedContent) && !isCharacterSmartReplaceExemptConsideringNonBreakingSpace(characterAfter(endOfInsertedContent), false);
     if (needsTrailingSpace && endNode) {
         bool collapseWhiteSpace = !endNode->layoutObject() || endNode->layoutObject()->style()->collapseWhiteSpace();
         if (endNode->isTextNode()) {
             insertTextIntoNode(toText(endNode), endOffset, collapseWhiteSpace ? nonBreakingSpaceString() : " ");
             if (m_endOfInsertedContent.computeContainerNode() == endNode)
                 m_endOfInsertedContent = Position(endNode, m_endOfInsertedContent.offsetInContainerNode() + 1);
         } else {
             Text* node = document().createEditingTextNode(collapseWhiteSpace ? nonBreakingSpaceString() : " ");
             insertNodeAfter(node, endNode, editingState);
             if (editingState->isAborted())
                 return;
             updateNodesInserted(node);
         }
     }
 
     document().updateStyleAndLayout();
 
+    VisiblePosition startOfInsertedContent = positionAtStartOfInsertedContent();

[yosin_UTC9, 2016/09/27 08:30:53]

This moving may change behavior due by DOM tree modification between L1473 to
L1496

[Xiaocheng, 2016/09/27 08:48:51]

DCHECK has been added to make sure that |m_startOfInsertedContent| remains the
same, and hence, moving the creation of |startOfInsertedContent| does not change
behvior.

     Position startDownstream = mostForwardCaretPosition(startOfInsertedContent.deepEquivalent());
     Node* startNode = startDownstream.computeNodeAfterPosition();
     unsigned startOffset = 0;
     if (startDownstream.isOffsetInAnchor()) {
         startNode = startDownstream.computeContainerNode();
         startOffset = startDownstream.offsetInContainerNode();
     }
 
     bool needsLeadingSpace = !isStartOfParagraphDeprecated(startOfInsertedContent) && !isCharacterSmartReplaceExemptConsideringNonBreakingSpace(characterBefore(startOfInsertedContent), true);
     if (needsLeadingSpace && startNode) {
@@ skipping 247 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