Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/styled_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_UI_COCOA_STYLED_TEXT_FIELD_H_
+#define CHROME_BROWSER_UI_COCOA_STYLED_TEXT_FIELD_H_
+
 #import <Cocoa/Cocoa.h>
 
 @class StyledTextFieldCell;
 
 // An implementation of NSTextField that is designed to work with
 // StyledTextFieldCell.  Provides methods to redraw the field when cell
 // decorations have changed and overrides |mouseDown:| to properly handle clicks
 // in sections of the cell with decorations.
 @interface StyledTextField : NSTextField {
 }
 
 // Repositions and redraws the field editor.  Call this method when the cell's
 // text frame has changed (whenever changing cell decorations).
 - (void)resetFieldEditorFrameIfNeeded;
 
 // Returns the amount of the field's width which is not being taken up
 // by the text contents.  May be negative if the contents are large
 // enough to scroll.
 - (CGFloat)availableDecorationWidth;
 
 @end
 
 @interface StyledTextField (ExposedForTesting)
 - (StyledTextFieldCell*)styledTextFieldCell;
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_STYLED_TEXT_FIELD_H_