Add mock classes for Bus, ObjectProxy, and ExportedObject.

Also add mock_unittest.cc that demonstrates how to mock synchronos and
asynchronos D-Bus method calls.

BUG=90036
TEST=dbus_unittests

Review URL: http://codereview.chromium.org/7714030

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@98188 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/dbus/exported_object.h b/dbus/exported_object.h
index 1351824c..d9cda576 100644
--- a/dbus/exported_object.h
+++ b/dbus/exported_object.h
@@ -86,9 +86,12 @@
   // BLOCKING CALL.
   virtual void Unregister();
 
+ protected:
+  // This is protected, so we can define sub classes.
+  virtual ~ExportedObject();
+
  private:
   friend class base::RefCountedThreadSafe<ExportedObject>;
-  virtual ~ExportedObject();
 
   // Helper function for ExportMethod().
   void ExportMethodInternal(const std::string& interface_name,