bluetoothLowEnergy: Send onServiceAdded after all characteristics are discovered

chromeos/dbus/bluetooth_gatt_characteristic_client.h

Index: chromeos/dbus/bluetooth_gatt_characteristic_client.h
diff --git a/chromeos/dbus/bluetooth_gatt_characteristic_client.h b/chromeos/dbus/bluetooth_gatt_characteristic_client.h
index 29b339a26ee40e80d8ea861490323b82f55526d0..ab5fd702dfb03f5175c0d59fff906da4c589f59b 100644
--- a/chromeos/dbus/bluetooth_gatt_characteristic_client.h
+++ b/chromeos/dbus/bluetooth_gatt_characteristic_client.h
@@ -30,7 +30,7 @@ class CHROMEOS_EXPORT BluetoothGattCharacteristicClient : public DBusClient {
     dbus::Property<dbus::ObjectPath> service;
 
     // Whether or not this characteristic is currently sending ValueUpdated
-    // signals.
+    // signals. [read-only]
     dbus::Property<bool> notifying;
 
     // List of flags representing the GATT "Characteristic Properties bit field"
@@ -38,6 +38,10 @@ class CHROMEOS_EXPORT BluetoothGattCharacteristicClient : public DBusClient {
     // descriptor bit field. [read-only, optional]
     dbus::Property<std::vector<std::string> > flags;
 
+    // Array of object paths representing the descriptors of this
+    // characteristic. [read-only]
+    dbus::Property<std::vector<dbus::ObjectPath> > descriptors;
+
     Properties(dbus::ObjectProxy* object_proxy,
                const std::string& interface_name,
                const PropertyChangedCallback& callback);