MD Settings: clarify "controlled by" logic

chrome/browser/extensions/api/settings_private/prefs_util.h

 // Copyright 2015 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_
 #define CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_
 
 #include <map>
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "chrome/common/extensions/api/settings_private.h"
 
 class PrefService;
 class Profile;
 
 namespace extensions {
+class Extension;
 
 class PrefsUtil {
 
  public:
   // Success or error statuses from calling SetPref.
   enum SetPrefResult {
     SUCCESS,
     PREF_NOT_MODIFIABLE,
     PREF_NOT_FOUND,
     PREF_TYPE_MISMATCH,
@@ skipping 65 matching lines @@
 
   api::settings_private::PrefType GetType(const std::string& name,
                                           base::Value::Type type);
 
   std::unique_ptr<api::settings_private::PrefObject> GetCrosSettingsPref(
       const std::string& name);
 
   SetPrefResult SetCrosSettingsPref(const std::string& name,
                                     const base::Value* value);
 
+ private:
+  const Extension* GetExtensionControllingPref(
+      const api::settings_private::PrefObject& pref_object);
+
   Profile* profile_;  // weak
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_SETTINGS_PRIVATE_PREFS_UTIL_H_