Make "Undo" command to restore selection after validating with the latest Layout tree

third_party/WebKit/Source/core/editing/VisibleSelection.cpp

 /*
  * Copyright (C) 2004, 2005, 2006 Apple Computer, 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 712 matching lines @@
     return isRichlyEditablePosition(toPositionInDOMTree(start()));
 }
 
 template <typename Strategy>
 Element* VisibleSelectionTemplate<Strategy>::rootEditableElement() const
 {
     return rootEditableElementOf(start());
 }
 
 template <typename Strategy>
-static bool isValidPosition(const PositionTemplate<Strategy>& position)
-{
-    if (!position.isConnected())
-        return false;
-
-    if (!position.isOffsetInAnchor())
-        return true;
-
-    if (position.offsetInContainerNode() < 0)
-        return false;
-
-    const unsigned offset = static_cast<unsigned>(position.offsetInContainerNode());
-    const unsigned nodeLength = position.anchorNode()->lengthOfContents();
-    return offset <= nodeLength;
-}
-
-template <typename Strategy>
 void VisibleSelectionTemplate<Strategy>::updateIfNeeded()
 {
     Document* document = m_base.document();
     if (!document)
         return;
     document->updateStyleAndLayoutIgnorePendingStylesheets();
     const bool hasTrailingWhitespace = m_hasTrailingWhitespace;
     validate(m_granularity);
     if (!hasTrailingWhitespace)
         return;
     appendTrailingWhitespace();
 }
 
+// TODO(yosin): Since |validatePositionsIfNeeded()| is called just one place,
+// we should move it to the call site.
 template <typename Strategy>
 void VisibleSelectionTemplate<Strategy>::validatePositionsIfNeeded()
 {
     if (!m_base.isConnected() || !m_extent.isConnected()) {
         *this = VisibleSelectionTemplate();
         return;
     }
-    if (isValidPosition(m_base) && isValidPosition(m_extent) && isValidPosition(m_start) && isValidPosition(m_end))
-        return;
-    validate();
+    updateIfNeeded();
 }
 
 template <typename Strategy>
 static bool equalSelectionsAlgorithm(const VisibleSelectionTemplate<Strategy>& selection1, const VisibleSelectionTemplate<Strategy>& selection2)
 {
     if (selection1.affinity() != selection2.affinity() || selection1.isDirectional() != selection2.isDirectional())
         return false;
 
     if (selection1.isNone())
         return selection2.isNone();
@@ skipping 125 matching lines @@
 {
     sel.showTreeForThis();
 }
 
 void showTree(const blink::VisibleSelectionInFlatTree* sel)
 {
     if (sel)
         sel->showTreeForThis();
 }
 #endif