Minor improvements on resource-policy interfaces

Change-Id: I3e9c7c4d1fca90e0fb97b0058e9b5a5e34940025
Reviewed-by: Michael Goddard <michael.goddard@nokia.com>
Reviewed-by: Dmytro Poplavskiy <dmytro.poplavskiy@nokia.com>
Reviewed-by: Jonas Rabbe <jonas.rabbe@nokia.com>

src/multimedia/qmediaresourceset_p.h

@@ -65,6 +65,8 @@ public:
     virtual void release() = 0;
     virtual void setVideoEnabled(bool enabled) = 0;
 
+    static QString iid();
+
 Q_SIGNALS:
     void resourcesGranted();
     void resourcesLost();