buffet: Stub for StartDevice method.

This introduces StartDevice method with stub implementation
and allows buffet_client to invoke it.

BUG=None
TEST=cros_workon_make buffet --test and manual.

Change-Id: I3f89ed3fc735c0521041484bb9fdebc43d9d4b79
Reviewed-on: https://chromium-review.googlesource.com/220771
Commit-Queue: Anton Muhin <antonm@chromium.org>
Tested-by: Anton Muhin <antonm@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/manager.h b/buffet/manager.h
index 4648b95..8d7ab13 100644
--- a/buffet/manager.h
+++ b/buffet/manager.h
@@ -43,6 +43,8 @@
 
  private:
   // DBus methods:
+  // Handles calls to org.chromium.Buffet.Manager.StartDevice().
+  void HandleStartDevice(chromeos::ErrorPtr* error);
   // Handles calls to org.chromium.Buffet.Manager.CheckDeviceRegistered().
   std::string HandleCheckDeviceRegistered(chromeos::ErrorPtr* error);
   // Handles calls to org.chromium.Buffet.Manager.GetDeviceInfo().