commonsys-intf: add split window interface.

Add an interface which allow users to get split window layers info.

Change-Id: Ifca373901498aaa3102d9a025ad79d1ffb4436e6
diff --git a/include/layer_extn_intf.h b/include/layer_extn_intf.h
index 04cbc98..adf36bb 100644
--- a/include/layer_extn_intf.h
+++ b/include/layer_extn_intf.h
@@ -50,6 +50,7 @@
  public:
   virtual ~LayerExtnIntf() = default;
   virtual int GetLayerClass(const std::string &name) = 0;
+  virtual void UpdateLayerState(const std::vector<std::string> &layers, int num_layers) = 0;
 };
 
 typedef bool (*CreateLayerExtnInterface)(uint16_t version, LayerExtnIntf **interface);