MD Settings: clarify "controlled by" logic

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

Index: chrome/browser/extensions/api/settings_private/prefs_util.h
diff --git a/chrome/browser/extensions/api/settings_private/prefs_util.h b/chrome/browser/extensions/api/settings_private/prefs_util.h
index 321a5c9e88f57e63d3086b7e640d3559ddc2b8d7..a2f229e0862f53615a0d2b528c55bd518580e57f 100644
--- a/chrome/browser/extensions/api/settings_private/prefs_util.h
+++ b/chrome/browser/extensions/api/settings_private/prefs_util.h
@@ -17,6 +17,7 @@ class PrefService;
 class Profile;
 
 namespace extensions {
+class Extension;
 
 class PrefsUtil {
 
@@ -102,6 +103,10 @@ class PrefsUtil {
   SetPrefResult SetCrosSettingsPref(const std::string& name,
                                     const base::Value* value);
 
+ private:
+  const Extension* GetExtensionControllingPref(
+      const api::settings_private::PrefObject& pref_object);
+
   Profile* profile_;  // weak
 };