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/shill_proxy_interface.h b/shill_proxy_interface.h
new file mode 100644
index 0000000..a4d3aa3
--- /dev/null
+++ b/shill_proxy_interface.h
@@ -0,0 +1,44 @@
+// Copyright 2015 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UPDATE_ENGINE_SHILL_PROXY_INTERFACE_H_
+#define UPDATE_ENGINE_SHILL_PROXY_INTERFACE_H_
+
+#include <memory>
+#include <string>
+
+#include <base/macros.h>
+
+#include "update_engine/dbus_proxies.h"
+
+namespace chromeos_update_engine {
+
+// This class handles the DBus connection with shill daemon. The DBus interface
+// with shill requires to monitor or request the current service by interacting
+// with the org::chromium::flimflam::ManagerProxy and then request or monitor
+// properties on the selected org::chromium::flimflam::ServiceProxy. This class
+// provides a mockable way to access that.
+class ShillProxyInterface {
+ public:
+  virtual ~ShillProxyInterface() = default;
+
+  // Return the ManagerProxy instance of the shill daemon. The instance is owned
+  // by this ShillProxyInterface instance.
+  virtual org::chromium::flimflam::ManagerProxyInterface* GetManagerProxy() = 0;
+
+  // Return a ServiceProxy for the given path. The ownership of the returned
+  // instance is transferred to the caller.
+  virtual std::unique_ptr<org::chromium::flimflam::ServiceProxyInterface>
+  GetServiceForPath(const std::string& path) = 0;
+
+ protected:
+  ShillProxyInterface() = default;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ShillProxyInterface);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_SHILL_PROXY_INTERFACE_H_