Don't over split DOM tree in CompositeEditCommand::splitTreeToNode

Source/core/editing/CompositeEditCommand.cpp

 /*
  * Copyright (C) 2005, 2006, 2007, 2008 Apple 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 1438 matching lines @@
 }
 
 // Splits the tree parent by parent until we reach the specified ancestor. We use VisiblePositions
 // to determine if the split is necessary. Returns the last split node.
 PassRefPtr<Node> CompositeEditCommand::splitTreeToNode(Node* start, Node* end, bool shouldSplitAncestor)
 {
     ASSERT(start);
     ASSERT(end);
     ASSERT(start != end);
 
-    RefPtr<Node> node;
     if (shouldSplitAncestor && end->parentNode())
         end = end->parentNode();
+    if (!start->isDescendantOf(end))
+        return end;
 
     RefPtr<Node> endNode = end;
-    for (node = start; node && node->parentNode() != endNode; node = node->parentNode()) {
+    RefPtr<Node> node;
+    for (node = start; node->parentNode() != endNode; node = node->parentNode()) {
         if (!node->parentNode()->isElementNode())
             break;
         // Do not split a node when doing so introduces an empty node.
         VisiblePosition positionInParent(firstPositionInNode(node->parentNode()));
         VisiblePosition positionInNode(firstPositionInOrBeforeNode(node.get()));
         if (positionInParent != positionInNode)
             splitElement(toElement(node->parentNode()), node);
     }
 
     return node.release();
 }
 
 PassRefPtrWillBeRawPtr<Element> createBlockPlaceholderElement(Document& document)
 {
     return document.createElement(brTag, false);
 }
 
 } // namespace WebCore