Get rid of sync_preferences::SyncedPrefObserver inheritance.

chrome/browser/chromeos/arc/arc_session_manager.h

Index: chrome/browser/chromeos/arc/arc_session_manager.h
diff --git a/chrome/browser/chromeos/arc/arc_session_manager.h b/chrome/browser/chromeos/arc/arc_session_manager.h
index 0bb3697ad151fc1fcfd3c28d398953fdd83246fa..c83dc84ccc3cd8e66f462a853a9f9cabcc29ada3 100644
--- a/chrome/browser/chromeos/arc/arc_session_manager.h
+++ b/chrome/browser/chromeos/arc/arc_session_manager.h
@@ -18,7 +18,6 @@
 #include "components/arc/arc_session_observer.h"
 #include "components/prefs/pref_change_registrar.h"
 #include "components/sync_preferences/pref_service_syncable_observer.h"
-#include "components/sync_preferences/synced_pref_observer.h"
 
 class ArcAppLauncher;
 class Profile;
@@ -44,8 +43,7 @@ enum class ProvisioningResult : int;
 // LSO. It lives on the UI thread.
 class ArcSessionManager : public ArcSessionObserver,
                           public ArcSupportHost::Observer,
-                          public sync_preferences::PrefServiceSyncableObserver,
-                          public sync_preferences::SyncedPrefObserver {
+                          public sync_preferences::PrefServiceSyncableObserver {
  public:
   // Represents each State of ARC session.
   // NOT_INITIALIZED: represents the state that the Profile is not yet ready
@@ -183,9 +181,6 @@ class ArcSessionManager : public ArcSessionObserver,
   // sync_preferences::PrefServiceSyncableObserver
   void OnIsSyncingChanged() override;
 
-  // sync_preferences::SyncedPrefObserver
-  void OnSyncedPrefChanged(const std::string& path, bool from_sync) override;
-
   // ArcSupportHost::Observer:
   void OnWindowClosed() override;
   void OnTermsAgreed(bool is_metrics_enabled,