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/chrome_browser_proxy_resolver.h b/chrome_browser_proxy_resolver.h
index 61f5982..1783aef 100644
--- a/chrome_browser_proxy_resolver.h
+++ b/chrome_browser_proxy_resolver.h
@@ -12,7 +12,7 @@
 #include <dbus/dbus-glib-lowlevel.h>
 #include <gtest/gtest_prod.h>  // for FRIEND_TEST
 
-#include "update_engine/dbus_interface.h"
+#include "update_engine/dbus_wrapper_interface.h"
 #include "update_engine/proxy_resolver.h"
 
 namespace chromeos_update_engine {
@@ -27,7 +27,7 @@
 
 class ChromeBrowserProxyResolver : public ProxyResolver {
  public:
-  explicit ChromeBrowserProxyResolver(DbusGlibInterface* dbus);
+  explicit ChromeBrowserProxyResolver(DBusWrapperInterface* dbus);
   virtual ~ChromeBrowserProxyResolver();
   bool Init();
 
@@ -75,7 +75,7 @@
   // Shutdown the dbus proxy object.
   void Shutdown();
 
-  DbusGlibInterface* dbus_;
+  DBusWrapperInterface* dbus_;
   DBusGProxy* proxy_;
   DBusGProxy* peer_proxy_;
   int timeout_;