Create c/b/ui/cocoa/test and move test files to there

chrome/browser/ui/cocoa/test/styled_text_field_test_helper.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.
 
 #import <Cocoa/Cocoa.h>
 #import "chrome/browser/ui/cocoa/styled_text_field_cell.h"
 
 // Subclass of StyledTextFieldCell that allows you to slice off sections on the
 // left and right of the cell.
 @interface StyledTextFieldTestCell : StyledTextFieldCell {
   CGFloat leftMargin_;
   CGFloat rightMargin_;
 }
 @property(nonatomic, assign) CGFloat leftMargin;
 @property(nonatomic, assign) CGFloat rightMargin;
 @end