Remove ArcSessionManager::Observer::OnArcBridgeShutdown.

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 7c97cdc1aaabc2c93fa74e8e5700f3ff54e016fe..58bc202e623430e60bc256b02342f86b8e1e4081 100644
--- a/chrome/browser/chromeos/arc/arc_session_manager.h
+++ b/chrome/browser/chromeos/arc/arc_session_manager.h
@@ -90,10 +90,6 @@ class ArcSessionManager : public ArcSessionObserver,
    public:
     virtual ~Observer() = default;
 
-    // Called to notify that ARC session is shut down.
-    // TODO(hidehiko): Rename the observer callback to OnArcSessionShutdown().
-    virtual void OnArcBridgeShutdown() {}
-
     // Called to notify that whether Google Play Store is enabled or not, which
     // is represented by "arc.enabled" preference, is updated.
     virtual void OnArcPlayStoreEnabledChanged(bool enabled) {}