[Mac] Support undo in the omnibox.

chrome/browser/cocoa/autocomplete_text_field.h

 // Copyright (c) 2009 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 CHROME_BROWSER_COCOA_AUTOCOMPLETE_TEXT_FIELD_H_
 #define CHROME_BROWSER_COCOA_AUTOCOMPLETE_TEXT_FIELD_H_
 
 #import <Cocoa/Cocoa.h>
 #import "chrome/browser/cocoa/styled_text_field.h"
 
+#include "base/scoped_nsobject.h"
+
 @class AutocompleteTextFieldCell;
 
 // AutocompleteTextField intercepts UI actions for forwarding to
 // AutocompleteEditViewMac (*), and provides a custom look.  It works
 // together with AutocompleteTextFieldEditor (mostly for intercepting
 // user actions) and AutocompleteTextFieldCell (mostly for custom
 // drawing).
 //
 // For historical reasons, chrome/browser/autocomplete is the core
 // implementation of the Omnibox.  Chrome code seems to vary between
@@ skipping 27 matching lines @@
   // Called when the user initiates a "paste and go" or "paste and
   // search" into |field_|.
   virtual void OnPasteAndGo() = 0;
 
   // Called when the field's frame changes.
   virtual void OnFrameChanged() = 0;
 };
 
 @interface AutocompleteTextField : StyledTextField {
  @private
+  // Undo manager for this text field.  We use a specific instance rather than
+  // the standard undo manager in order to let us clear the undo stack at will.
+  scoped_nsobject<NSUndoManager> undoManager_;
+
   AutocompleteTextFieldObserver* observer_;  // weak, owned by location bar.
 }
 
 @property AutocompleteTextFieldObserver* observer;
 
 // Convenience method to return the cell, casted appropriately.
 - (AutocompleteTextFieldCell*)autocompleteTextFieldCell;
 
 // Superclass aborts editing before changing the string, which causes
 // problems for undo.  This version modifies the field editor's
 // contents if the control is already being edited.
 - (void)setAttributedStringValue:(NSAttributedString*)aString;
 
+// Clears the undo chain for this text field.
+- (void)clearUndoChain;
+
 @end
 
 #endif  // CHROME_BROWSER_COCOA_AUTOCOMPLETE_TEXT_FIELD_H_