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.h b/update_attempter.h
index d5c6adb..d93c049 100644
--- a/update_attempter.h
+++ b/update_attempter.h
@@ -60,7 +60,7 @@
   static const int kMaxDeltaUpdateFailures;
 
   UpdateAttempter(SystemState* system_state,
-                  DbusGlibInterface* dbus_iface);
+                  DBusWrapperInterface* dbus_iface);
   virtual ~UpdateAttempter();
 
   // Checks for update and, if a newer version is available, attempts to update
@@ -193,7 +193,7 @@
 
   // Special ctor + friend declarations for testing purposes.
   UpdateAttempter(SystemState* system_state,
-                  DbusGlibInterface* dbus_iface,
+                  DBusWrapperInterface* dbus_iface,
                   const std::string& update_completed_marker);
 
   friend class UpdateAttempterUnderTest;