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

components/update_client/ping_manager.cc

Index: components/update_client/ping_manager.cc
diff --git a/components/update_client/ping_manager.cc b/components/update_client/ping_manager.cc
index 7d05e5a82b47aaf74b07b6762c66c59ef3d9902c..17bcdd610591fd03d51d999b6a3b474306255375 100644
--- a/components/update_client/ping_manager.cc
+++ b/components/update_client/ping_manager.cc
@@ -164,7 +164,8 @@ std::string BuildPing(const Configurator& config, const CrxUpdateItem* item) {
 
   return BuildProtocolRequest(config.GetBrowserVersion().GetString(),
                               config.GetChannel(), config.GetLang(),
-                              config.GetOSLongName(), app_element, "");
+                              config.GetOSLongName(),
+                              config.GetDownloadPreference(), app_element, "");
 }
 
 // Sends a fire and forget ping. The instances of this class have no