Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.h

Index: chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.h
diff --git a/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.h b/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.h
index f5073a7fcd415b4b83da362a9be21b070db62315..3b760e71fd2b8cf56554b725bad63c68fd4f111b 100644
--- a/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.h
+++ b/chrome/browser/ui/cocoa/bookmarks/bookmark_bubble_controller.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_BOOKMARKS_BOOKMARK_BUBBLE_CONTROLLER_H_
+#define CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_BUBBLE_CONTROLLER_H_
+
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ -94,3 +97,5 @@ class ManagedBookmarkService;
 + (NSString*)chooseAnotherFolderString;
 - (NSPopUpButton*)folderPopUpButton;
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_BOOKMARKS_BOOKMARK_BUBBLE_CONTROLLER_H_