device/bluetooth/bluez: add discoverable timeout adapter property

device/bluetooth/bluetooth_adapter_unittest.cc

Index: device/bluetooth/bluetooth_adapter_unittest.cc
diff --git a/device/bluetooth/bluetooth_adapter_unittest.cc b/device/bluetooth/bluetooth_adapter_unittest.cc
index d7948bf56f000f453faca6e3dc76894d8300f12c..e06f9c52294fc236c45186dea5e7a47f21a5ea88 100644
--- a/device/bluetooth/bluetooth_adapter_unittest.cc
+++ b/device/bluetooth/bluetooth_adapter_unittest.cc
@@ -68,6 +68,8 @@ class TestBluetoothAdapter : public BluetoothAdapter {
                        const base::Closure& callback,
                        const ErrorCallback& error_callback) override {}
 
+  uint32_t GetDiscoverableTimeout() const override { return 0; }
+
   bool IsDiscovering() const override { return false; }
 
   void StartDiscoverySessionWithFilter(