Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h

Index: chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h
diff --git a/chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h b/chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h
index 8ece57240ec85353a07227c45f69f61fa2239af3..97ca8844718f73c8501c9749e55dbdd7619eab7f 100644
--- a/chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h
+++ b/chrome/browser/ui/cocoa/test/styled_text_field_test_helper.h
@@ -2,6 +2,9 @@
 // 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_TEST_STYLED_TEXT_FIELD_TEST_HELPER_H_
+#define CHROME_BROWSER_UI_COCOA_TEST_STYLED_TEXT_FIELD_TEST_HELPER_H_
+
 #import <Cocoa/Cocoa.h>
 #import "chrome/browser/ui/cocoa/styled_text_field_cell.h"
 
@@ -14,3 +17,5 @@
 @property(nonatomic, assign) CGFloat leftMargin;
 @property(nonatomic, assign) CGFloat rightMargin;
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_TEST_STYLED_TEXT_FIELD_TEST_HELPER_H_