Add missing include guards in Cocoa code.

chrome/browser/ui/cocoa/base_bubble_controller.h

Index: chrome/browser/ui/cocoa/base_bubble_controller.h
diff --git a/chrome/browser/ui/cocoa/base_bubble_controller.h b/chrome/browser/ui/cocoa/base_bubble_controller.h
index 1314263b15a635bcb0d33ea28f364c90e7ee015e..9065d9e1daf2d0875bc28c51daaa104fd1639ad6 100644
--- a/chrome/browser/ui/cocoa/base_bubble_controller.h
+++ b/chrome/browser/ui/cocoa/base_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_BASE_BUBBLE_CONTROLLER_H_
+#define CHROME_BROWSER_UI_COCOA_BASE_BUBBLE_CONTROLLER_H_
+
 #import <Cocoa/Cocoa.h>
 
 #include <memory>
@@ -109,3 +112,5 @@ class TabStripModelObserverBridge;
 // |-showWindow:| is overriden and does not call super. Noop on OSes <10.7.
 - (void)registerKeyStateEventTap;
 @end
+
+#endif  // CHROME_BROWSER_UI_COCOA_BASE_BUBBLE_CONTROLLER_H_