Remove unused DBusThreadManagerObserver

chromeos/dbus/dbus_thread_manager.h

Index: chromeos/dbus/dbus_thread_manager.h
diff --git a/chromeos/dbus/dbus_thread_manager.h b/chromeos/dbus/dbus_thread_manager.h
index f225a5e14ca74b3c1ad78b3df97b688de0865bbd..2a5e335bf056327c13a7134190d43c2f9cf3bddd 100644
--- a/chromeos/dbus/dbus_thread_manager.h
+++ b/chromeos/dbus/dbus_thread_manager.h
@@ -21,8 +21,6 @@ class ObjectPath;
 
 namespace chromeos {
 
-class DBusThreadManagerObserver;
-
 // Style Note: Clients are sorted by names.
 class BluetoothAdapterClient;
 class BluetoothAgentManagerClient;
@@ -116,10 +114,6 @@ class CHROMEOS_EXPORT DBusThreadManager {
   // Gets the global instance. Initialize() must be called first.
   static DBusThreadManager* Get();
 
-  // Adds or removes an observer.
-  virtual void AddObserver(DBusThreadManagerObserver* observer) = 0;
-  virtual void RemoveObserver(DBusThreadManagerObserver* observer) = 0;
-
   // Returns various D-Bus bus instances, owned by DBusThreadManager.
   virtual dbus::Bus* GetSystemBus() = 0;