update_engine: Switch to chrome-dbus for client requests in update_engine

update_engine daemon acts as DBus client to send DBus calls to shill,
power_manager and chrome, and to listen for signals from shill, chrome
and login_manager. This patch migrates these calls and signals to use
chrome-dbus framework instead of dbus-glib.

All references to dbus-glib code are removed.

BUG=chromium:419827
TEST=Updated unittest. Deployed on a link device and tested interactions with shill and chromium.

Change-Id: I31b389e0d1690cccb115ff3b6539c876ba81bd0e
Reviewed-on: https://chromium-review.googlesource.com/290990
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
Trybot-Ready: Alex Deymo <deymo@chromium.org>
diff --git a/omaha_request_action.cc b/omaha_request_action.cc
index 2f361e5..3d7cccc 100644
--- a/omaha_request_action.cc
+++ b/omaha_request_action.cc
@@ -29,7 +29,6 @@
 #include "update_engine/p2p_manager.h"
 #include "update_engine/payload_state_interface.h"
 #include "update_engine/prefs_interface.h"
-#include "update_engine/real_dbus_wrapper.h"
 #include "update_engine/utils.h"
 
 using base::Time;
@@ -1448,11 +1447,9 @@
 bool OmahaRequestAction::IsUpdateAllowedOverCurrentConnection() const {
   NetworkConnectionType type;
   NetworkTethering tethering;
-  RealDBusWrapper dbus_iface;
   ConnectionManagerInterface* connection_manager =
       system_state_->connection_manager();
-  if (!connection_manager->GetConnectionProperties(&dbus_iface,
-                                                   &type, &tethering)) {
+  if (!connection_manager->GetConnectionProperties(&type, &tethering)) {
     LOG(INFO) << "We could not determine our connection type. "
               << "Defaulting to allow updates.";
     return true;