As discussed in http://b/112468968#comment17, it looks like Chrome's chromeos::CrosDBusService class's Start method calls dbus::Bus::RequestOwnership before giving ServiceProviderInterface implementations a chance to export methods:

chromeos/dbus/services/cros_dbus_service.cc:

 42   // Starts the D-Bus service.
 43   void Start() {
...
 57     bus_->RequestOwnership(
 58         service_name_, dbus::Bus::REQUIRE_PRIMARY_ALLOW_REPLACEMENT,
 59         base::Bind(&CrosDBusServiceImpl::OnOwnership, base::Unretained(this)));
 60 
 61     exported_object_ = bus_->GetExportedObject(object_path_);
 62     for (size_t i = 0; i < service_providers_.size(); ++i)
 63       service_providers_[i]->Start(exported_object_);

This creates a window where the service name is owned but the methods are not yet exported. If other D-Bus clients try to call methods in response to the ownership change, their calls may fail due to the methods not existing. powerd made this mistake at one point too ( issue 331431 ).

I think that this method should be changed so that methods are exported before RequestOwnership is called.