Further cleanup around DBus interface classes.

* Removed the "Glib" part from the various DbusGlib class name and added
  "Wrapper" instead: only part of the methods here declared have
  anything to do with Glib; in essence, this is an interface containing
  wrappers for various DBus functions.

* Changed "Dbus" to "DBus", to comply with the rest of the world.

* Renamed the actual implementation "RealDBusWrapper" (instead of
  "Concrete").

* Separated out RealDBusWrapper into its own header file. Client code,
  which often only cares about the abstract class, does not need to pull
  it unless specifically requiring it.

* Cleaned up the includes in these headers.

Aside from all that, also renamed system_state.cc into
real_system_state.cc, as this is what this file contains.

BUG=None
TEST=Unit tests.

Change-Id: I015c407cbc159aba8b5925eb0e916ba604c829cd
Reviewed-on: https://chromium-review.googlesource.com/189373
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/update_attempter_unittest.cc b/update_attempter_unittest.cc
index 7031bb9..396b4a8 100644
--- a/update_attempter_unittest.cc
+++ b/update_attempter_unittest.cc
@@ -12,7 +12,7 @@
 #include "update_engine/fake_clock.h"
 #include "update_engine/filesystem_copier_action.h"
 #include "update_engine/install_plan.h"
-#include "update_engine/mock_dbus_interface.h"
+#include "update_engine/mock_dbus_wrapper.h"
 #include "update_engine/mock_http_fetcher.h"
 #include "update_engine/mock_p2p_manager.h"
 #include "update_engine/mock_payload_state.h"
@@ -48,11 +48,11 @@
   // explicitly specified, we feed an empty string, which causes the
   // UpdateAttempter class to ignore / not write the marker file.
   UpdateAttempterUnderTest(MockSystemState* mock_system_state,
-                           MockDbusGlib* dbus)
+                           MockDBusWrapper* dbus)
       : UpdateAttempter(mock_system_state, dbus, "") {}
 
   UpdateAttempterUnderTest(MockSystemState* mock_system_state,
-                           MockDbusGlib* dbus,
+                           MockDBusWrapper* dbus,
                            const string& update_completed_marker)
       : UpdateAttempter(mock_system_state, dbus, update_completed_marker) {}
 };
@@ -148,7 +148,7 @@
   static gboolean StaticP2PEnabledHousekeepingFails(gpointer data);
 
   NiceMock<MockSystemState> mock_system_state_;
-  NiceMock<MockDbusGlib> dbus_;
+  NiceMock<MockDBusWrapper> dbus_;
   UpdateAttempterUnderTest attempter_;
   NiceMock<ActionProcessorMock>* processor_;
   NiceMock<PrefsMock>* prefs_; // shortcut to mock_system_state_->mock_prefs()