Clear undo stack when text control is set programatically

Source/core/editing/Editor.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  *
  * 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 935 matching lines @@
         return undoStack->canRedo();
     return false;
 }
 
 void Editor::redo()
 {
     if (UndoStack* undoStack = this->undoStack())
         undoStack->redo();
 }
 
+void Editor::clearUndoStack()
+{
+    if (UndoStack* undoStack = this->undoStack())
+        undoStack->clear();
+}
+
 void Editor::setBaseWritingDirection(WritingDirection direction)
 {
     Node* focusedElement = frame().document()->focusedElement();
     if (focusedElement && isHTMLTextFormControlElement(*focusedElement)) {
         if (direction == NaturalWritingDirection)
             return;
         toHTMLElement(focusedElement)->setAttribute(dirAttr, direction == LeftToRightWritingDirection ? "ltr" : "rtl");
         focusedElement->dispatchInputEvent();
         frame().document()->updateStyleIfNeeded();
         return;
@@ skipping 265 matching lines @@
     return m_frame.spellChecker();
 }
 
 void Editor::toggleOverwriteModeEnabled()
 {
     m_overwriteModeEnabled = !m_overwriteModeEnabled;
     frame().selection().setShouldShowBlockCursor(m_overwriteModeEnabled);
 }
 
 } // namespace WebCore