update_engine: Use org.chromium.KioskAppService service.

Make update_engine use the org.chromium.KioskAppService
D-Bus service exported by Chrome rather than the old methods
under org.chromium.LibCrosService.

BUG=chromium:703229
TEST=unit tests pass; also hacked up RealSystemProvider to
     call its GetKioskAppRequiredPlatformVersion and
     manually verified that the D-Bus call succeeds

Change-Id: I02d503da1e1aec2319c75e2237c87bfcdcd1f7e5
Reviewed-on: https://chromium-review.googlesource.com/987325
Commit-Ready: Dan Erat <derat@chromium.org>
Tested-by: Dan Erat <derat@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/real_system_state.cc b/real_system_state.cc
index 8e7ad51..b39b7b3 100644
--- a/real_system_state.cc
+++ b/real_system_state.cc
@@ -67,8 +67,8 @@
   }
 
 #if USE_CHROME_KIOSK_APP
-  libcros_proxy_.reset(new org::chromium::LibCrosServiceInterfaceProxy(
-      DBusConnection::Get()->GetDBus(), chromeos::kLibCrosServiceName));
+  kiosk_app_proxy_.reset(new org::chromium::KioskAppServiceInterfaceProxy(
+      DBusConnection::Get()->GetDBus(), chromeos::kKioskAppServiceName));
 #endif  // USE_CHROME_KIOSK_APP
 
   LOG_IF(INFO, !hardware_->IsNormalBootMode()) << "Booted in dev mode.";
@@ -150,7 +150,7 @@
   chromeos_update_manager::State* um_state =
       chromeos_update_manager::DefaultStateFactory(&policy_provider_,
 #if USE_CHROME_KIOSK_APP
-                                                   libcros_proxy_.get(),
+                                                   kiosk_app_proxy_.get(),
 #else
                                                    nullptr,
 #endif  // USE_CHROME_KIOSK_APP