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/test_utils.cc b/test_utils.cc
index 0c02279..b4a8074 100644
--- a/test_utils.cc
+++ b/test_utils.cc
@@ -19,8 +19,8 @@
 
 #include <base/files/file_util.h>
 #include <base/logging.h>
-#include <base/strings/stringprintf.h>
 #include <base/strings/string_util.h>
+#include <base/strings/stringprintf.h>
 
 #include "update_engine/file_writer.h"
 #include "update_engine/utils.h"
@@ -302,19 +302,6 @@
   return true;
 }
 
-GValue* GValueNewString(const char* str) {
-  GValue* gval = g_new0(GValue, 1);
-  g_value_init(gval, G_TYPE_STRING);
-  g_value_set_string(gval, str);
-  return gval;
-}
-
-void GValueFree(gpointer arg) {
-  auto gval = reinterpret_cast<GValue*>(arg);
-  g_value_unset(gval);
-  g_free(gval);
-}
-
 base::FilePath GetBuildArtifactsPath() {
   base::FilePath exe_path;
   base::ReadSymbolicLink(base::FilePath("/proc/self/exe"), &exe_path);