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

chrome/browser/extensions/extension_pref_value_map.h

Index: chrome/browser/extensions/extension_pref_value_map.h
diff --git a/chrome/browser/extensions/extension_pref_value_map.h b/chrome/browser/extensions/extension_pref_value_map.h
index e03123b56f6742018bf9e844f166523c400dd750..da24191222c868de053ce4d408f9ace43e91d863 100644
--- a/chrome/browser/extensions/extension_pref_value_map.h
+++ b/chrome/browser/extensions/extension_pref_value_map.h
@@ -116,6 +116,16 @@ class ExtensionPrefValueMap : public ProfileKeyedService {
                                 const std::string& pref_key,
                                 bool incognito) const;
 
+  // Returns true if an extension identified by |extension_id| controls the
+  // preference, *and* it is specific to incognito mode. This means this
+  // extension has set a preference value and no other extension with higher
+  // precedence overrides it.
+  // 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 DoesExtensionControlIncognitoPref(const std::string& extension_id,
+                                         const std::string& pref_key) const;
+
   // Tell the store it's now fully initialized.
   void NotifyInitializationCompleted();