Make SynchronousMutationObserver::didMergeTextNodes() to take both merged and merging nodes

third_party/WebKit/Source/core/dom/Text.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights
  * reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 64 matching lines @@
       continue;
     }
 
     // Both non-empty text nodes. Merge them.
     unsigned offset = length();
     String nextTextData = nextText->data();
     String oldTextData = data();
     setDataWithoutUpdate(data() + nextTextData);
     updateTextLayoutObject(oldTextData.length(), 0);
 
+    document().didMergeTextNodes(*this, *nextText, offset);
+
     // Empty nextText for layout update.
     nextText->setDataWithoutUpdate(emptyString());
     nextText->updateTextLayoutObject(0, nextTextData.length());
 
-    document().didMergeTextNodes(*nextText, offset);
-
     // Restore nextText for mutation event.
     nextText->setDataWithoutUpdate(nextTextData);
     nextText->updateTextLayoutObject(0, 0);
 
     document().incDOMTreeVersion();
     didModifyData(oldTextData, CharacterData::UpdateFromNonParser);
     nextText->remove(IGNORE_EXCEPTION_FOR_TESTING);
   }
 
   return NodeTraversal::nextPostOrder(*this);
@@ skipping 348 matching lines @@
 
 Text* Text::cloneWithData(const String& data) {
   return create(document(), data);
 }
 
 DEFINE_TRACE(Text) {
   CharacterData::trace(visitor);
 }
 
 }  // namespace blink