bluetooth: Add DeviceChanged logging in Device service.

device/bluetooth/device.h

Index: device/bluetooth/device.h
diff --git a/device/bluetooth/device.h b/device/bluetooth/device.h
index c82439e6c283ecb6e851e466061bedf060a18420..ed9b84e3bafb1d46af7698ce9180d5ea6a97863e 100644
--- a/device/bluetooth/device.h
+++ b/device/bluetooth/device.h
@@ -19,7 +19,7 @@ namespace bluetooth {
 // device/bluetooth/public/interfaces/device.mojom.
 // It handles requests to interact with Bluetooth Device.
 // Uses the platform abstraction of device/bluetooth.
-class Device : public mojom::Device {
+class Device : public mojom::Device, public device::BluetoothAdapter::Observer {
  public:
   Device(const std::string& address,
          scoped_refptr<device::BluetoothAdapter> adapter);
@@ -29,8 +29,13 @@ class Device : public mojom::Device {
   static mojom::DeviceInfoPtr ConstructDeviceInfoStruct(
       const device::BluetoothDevice* device);
 
+  // device::BluetoothAdapter::Observer overrides:
+  void DeviceChanged(device::BluetoothAdapter* adapter,
+                     device::BluetoothDevice* device) override;
+
   // mojom::Device overrides:
   void GetInfo(const GetInfoCallback& callback) override;
+  void SetClient(mojom::GattClientPtr client) override;
 
  private:
   // The address of the Bluetooth device.
@@ -39,6 +44,9 @@ class Device : public mojom::Device {
   // The current BluetoothAdapter.
   scoped_refptr<device::BluetoothAdapter> adapter_;
 
+  // The current client which listens to events from this device.
+  mojom::GattClientPtr client_;
+
   DISALLOW_COPY_AND_ASSIGN(Device);
 };