views::Textfield: Implement transpose editing command.

ui/views/controls/textfield/textfield_model.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_
 #define UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_
 
 #include <stddef.h>
 
 #include <list>
@@ skipping 159 matching lines @@
   bool Cut();
 
   // Copies the currently selected text and puts it to clipboard. Returns true
   // if something was copied to the clipboard.
   bool Copy();
 
   // Pastes text from the clipboard at current cursor position. Returns true
   // if any text is pasted.
   bool Paste();
 
+  // Transposes the characters to either side of the insertion point and
+  // advances the insertion point past both of them. Returns true if text is
+  // changed.
+  bool Transpose();
+
   // Tells if any text is selected, even if the selection is in composition
   // text.
   bool HasSelection() const;
 
   // Deletes the selected text. This method shouldn't be called with
   // composition text.
   void DeleteSelection();
 
   // Deletes the selected text (if any) and insert text at given position.
   void DeleteSelectionAndInsertTextAt(const base::string16& new_text,
@@ skipping 99 matching lines @@
   //   2) new edit is added. (redo history is cleared)
   //   3) redone all undone edits.
   EditHistory::iterator current_edit_;
 
   DISALLOW_COPY_AND_ASSIGN(TextfieldModel);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_TEXTFIELD_TEXTFIELD_MODEL_H_