Split mode incognito extension can get misleading pref changed events from regular mode

chrome/browser/extensions/extension_pref_value_map.h

 // Copyright (c) 2012 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_EXTENSION_PREF_VALUE_MAP_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_PREF_VALUE_MAP_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 90 matching lines @@
   // PrefService::Preference::IsExtensionModifiable() returns true as well.
   bool CanExtensionControlPref(const std::string& extension_id,
                                const std::string& pref_key,
                                bool incognito) const;
 
   // Removes all "incognito session only" preference values.
   void ClearAllIncognitoSessionOnlyPreferences();
 
   // Returns true if an extension identified by |extension_id| controls the
   // preference. This means this extension has set a preference value and no
-  // other extension with higher precedence overrides it.
+  // other extension with higher precedence overrides it. If |from_incognito|
+  // is not NULL, looks at incognito preferences first, and |from_incognito| is
+  // set to true if the effective pref value is coming from the incognito
+  // preferences, false if it is coming from the normal ones.
   // Note that the this function does does not consider the existence of
   // policies. An extension is only really able to control a preference if
   // PrefService::Preference::IsExtensionModifiable() returns true as well.
   bool DoesExtensionControlPref(const std::string& extension_id,
                                 const std::string& pref_key,
-                                bool incognito) const;
+                                bool* from_incognito) const;
 
   // Tell the store it's now fully initialized.
   void NotifyInitializationCompleted();
 
   // Registers the time when an extension |ext_id| is installed.
   void RegisterExtension(const std::string& ext_id,
                          const base::Time& install_time,
                          bool is_enabled);
 
   // Deletes all entries related to extension |ext_id|.
@@ skipping 53 matching lines @@
   // being destroyed. In tests, it isn't called, so the notification must
   // be done in the destructor. This bit tracks whether it has been done yet.
   bool destroyed_;
 
   ObserverList<Observer, true> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionPrefValueMap);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_PREF_VALUE_MAP_H_