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/libcurl_http_fetcher.cc b/libcurl_http_fetcher.cc
index b5c67e0..41927ca 100644
--- a/libcurl_http_fetcher.cc
+++ b/libcurl_http_fetcher.cc
@@ -12,8 +12,8 @@
 #include <base/stringprintf.h>
 
 #include "update_engine/certificate_checker.h"
-#include "update_engine/dbus_interface.h"
 #include "update_engine/hardware_interface.h"
+#include "update_engine/real_dbus_wrapper.h"
 #include "update_engine/utils.h"
 
 using google::protobuf::NewCallback;
@@ -40,7 +40,7 @@
 // On error, returns false.
 bool LibcurlHttpFetcher::IsUpdateAllowedOverCurrentConnection() const {
   NetworkConnectionType type;
-  ConcreteDbusGlib dbus_iface;
+  RealDBusWrapper dbus_iface;
   ConnectionManager* connection_manager = system_state_->connection_manager();
   if (!connection_manager->GetConnectionType(&dbus_iface, &type)) {
     LOG(INFO) << "We could not determine our connection type. "