bluetooth: Shutdown BluetoothAdapter before DBus on ChromeOS.

device/bluetooth/bluetooth_adapter_chromeos.h

Index: device/bluetooth/bluetooth_adapter_chromeos.h
diff --git a/device/bluetooth/bluetooth_adapter_chromeos.h b/device/bluetooth/bluetooth_adapter_chromeos.h
index 0bcd6f741fe3e52368fa1ce2f421971f3a3d8057..910494a92e206f8a21b774b06f77252b4d8b297a 100644
--- a/device/bluetooth/bluetooth_adapter_chromeos.h
+++ b/device/bluetooth/bluetooth_adapter_chromeos.h
@@ -44,6 +44,7 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterChromeOS
   static base::WeakPtr<BluetoothAdapter> CreateAdapter();
 
   // BluetoothAdapter:
+  void Shutdown() override;
   void DeleteOnCorrectThread() const override;
   virtual void AddObserver(
       device::BluetoothAdapter::Observer* observer) override;
@@ -241,6 +242,9 @@ class DEVICE_BLUETOOTH_EXPORT BluetoothAdapterChromeOS
   // ended (with either success or failure).
   void ProcessQueuedDiscoveryRequests();
 
+  // Set in |Shutdown()| and used to force |IsPresent()| to return false.
+  bool is_shutdown_;
+
   // Number of discovery sessions that have been added.
   int num_discovery_sessions_;