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..cbe5695e603547085df28cb3015e09fe75b6afba 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 +103,9 @@ class PrefsUtil {
   SetPrefResult SetCrosSettingsPref(const std::string& name,
                                     const base::Value* value);
 
+ private:
+  const Extension* GetExtensionControllingPref(const std::string& pref_name);
+
   Profile* profile_;  // weak
 };