Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.h

Index: chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.h
diff --git a/chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.h b/chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.h
index f602b69a5a41db6f5ed635684f99fc4c1887f44b..b9e827554713e3b93ee3c49e4820a0207abdb825 100644
--- a/chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.h
+++ b/chrome/browser/ui/cocoa/content_settings/collected_cookies_mac.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_CONTENT_SETTINGS_COLLECTED_COOKIES_MAC_H_
+#define CHROME_BROWSER_UI_COCOA_CONTENT_SETTINGS_COLLECTED_COOKIES_MAC_H_
+
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ -150,3 +153,5 @@ class CollectedCookiesMac : public ConstrainedWindowMacDelegate,
 + (NSArray*)normalizeNodeSelection:(NSArray*)selection;
 
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_CONTENT_SETTINGS_COLLECTED_COOKIES_MAC_H_