Make ReplaceSelectionCommand to handle empty SPAN replacement

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 1295 matching lines @@
     }
 
     makeInsertedContentRoundTrippableWithHTMLTreeBuilder(insertedNodes, editingState);
     if (editingState->isAborted())
         return;
 
     removeRedundantStylesAndKeepStyleSpanInline(insertedNodes, editingState);
     if (editingState->isAborted())
         return;
 
-    if (m_sanitizeFragment) {
+    if (m_sanitizeFragment && insertedNodes.firstNodeInserted()) {
         applyCommandToComposite(SimplifyMarkupCommand::create(document(), insertedNodes.firstNodeInserted(), insertedNodes.pastLastLeaf()), editingState);
         if (editingState->isAborted())
             return;
     }
 
     // Setup m_startOfInsertedContent and m_endOfInsertedContent. This should be the last two lines of code that access insertedNodes.
     m_startOfInsertedContent = firstPositionInOrBeforeNode(insertedNodes.firstNodeInserted());
     m_endOfInsertedContent = lastPositionInOrAfterNode(insertedNodes.lastLeafInserted());
 
     // Determine whether or not we should merge the end of inserted content with what's after it before we do
@@ skipping 429 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