arc: bluetooth: Add/Remove BT observer only when ARC is ready

device/bluetooth/bluetooth_adapter.cc

Index: device/bluetooth/bluetooth_adapter.cc
diff --git a/device/bluetooth/bluetooth_adapter.cc b/device/bluetooth/bluetooth_adapter.cc
index 7b30fad19ebd8a1f5ce5d300142767bf306fe234..878d3b4c9788205c2d14cbb2c0ac985a96a5d703 100644
--- a/device/bluetooth/bluetooth_adapter.cc
+++ b/device/bluetooth/bluetooth_adapter.cc
@@ -55,6 +55,11 @@ void BluetoothAdapter::RemoveObserver(BluetoothAdapter::Observer* observer) {
   observers_.RemoveObserver(observer);
 }
 
+bool BluetoothAdapter::HasObserver(BluetoothAdapter::Observer* observer) {
+  DCHECK(observer);
+  return observers_.HasObserver(observer);
+}
+
 void BluetoothAdapter::StartDiscoverySession(
     const DiscoverySessionCallback& callback,
     const ErrorCallback& error_callback) {