Implement the gattserverdisconnected event.

device/bluetooth/test/mock_bluetooth_device.h

Index: device/bluetooth/test/mock_bluetooth_device.h
diff --git a/device/bluetooth/test/mock_bluetooth_device.h b/device/bluetooth/test/mock_bluetooth_device.h
index f6e79ec5309353508ce49753971546b59a9ab62e..c07a17f0b7b8f4747ff724d29d0d446ea591e996 100644
--- a/device/bluetooth/test/mock_bluetooth_device.h
+++ b/device/bluetooth/test/mock_bluetooth_device.h
@@ -111,11 +111,14 @@ class MockBluetoothDevice : public BluetoothDevice {
   BluetoothRemoteGattService* GetMockService(
       const std::string& identifier) const;
 
+  void SetConnected(bool connected) { connected_ = connected; }
+
  private:
   uint32_t bluetooth_class_;
   std::string name_;
   std::string address_;
   BluetoothDevice::UUIDList uuids_;
+  bool connected_;
 
   ScopedVector<MockBluetoothGattService> mock_services_;
 };