Fix BluetoothConnection to disconnect when the underlying device disconnects.

components/proximity_auth/bluetooth_connection.cc

Index: components/proximity_auth/bluetooth_connection.cc
diff --git a/components/proximity_auth/bluetooth_connection.cc b/components/proximity_auth/bluetooth_connection.cc
index f06d52f6d260d05e435a8ebc3a091ecfe8425271..fbd548d1ac7527a9598a1bcf6dfc296cccb40c32 100644
--- a/components/proximity_auth/bluetooth_connection.cc
+++ b/components/proximity_auth/bluetooth_connection.cc
@@ -88,6 +88,16 @@ void BluetoothConnection::SendMessageImpl(scoped_ptr<WireMessage> message) {
                 base::Bind(&BluetoothConnection::OnSendError, weak_this));
 }
 
+void BluetoothConnection::DeviceChanged(device::BluetoothAdapter* adapter,
+                                        device::BluetoothDevice* device) {
+  DCHECK_EQ(adapter, adapter_.get());
+  if (device->GetAddress() == remote_device().bluetooth_address &&
+      IsConnected() && !device->IsConnected()) {
+    PA_LOG(INFO) << "Device disconnected...";
+    Disconnect();
+  }
+}
+
 void BluetoothConnection::DeviceRemoved(device::BluetoothAdapter* adapter,
                                         device::BluetoothDevice* device) {
   DCHECK_EQ(adapter, adapter_.get());