Implement Windows GPO support for "dlpref" in component updater.

components/component_updater/configurator_impl.cc

Index: components/component_updater/configurator_impl.cc
diff --git a/components/component_updater/configurator_impl.cc b/components/component_updater/configurator_impl.cc
index be529131ffff6fafe6f3df98341c7652d07bae7f..34097a00fac545793cd0a6e38cf6102f42113943 100644
--- a/components/component_updater/configurator_impl.cc
+++ b/components/component_updater/configurator_impl.cc
@@ -163,6 +163,10 @@ std::string ConfiguratorImpl::ExtraRequestParams() const {
   return extra_info_;
 }
 
+std::string ConfiguratorImpl::GetDownloadPreference() const {
+  return std::string();
+}
+
 net::URLRequestContextGetter* ConfiguratorImpl::RequestContext() const {
   return url_request_getter_;
 }