add support hwc 1.1

Bug: 7124069

Change-Id: I53d705105c4ad8954d3f50ee4f4c8b7ec936b871
diff --git a/services/surfaceflinger/Layer.h b/services/surfaceflinger/Layer.h
index b839f8c..6f75d8c 100644
--- a/services/surfaceflinger/Layer.h
+++ b/services/surfaceflinger/Layer.h
@@ -82,6 +82,7 @@
     virtual void onRemoved();
     virtual sp<Layer> getLayer() const { return const_cast<Layer*>(this); }
     virtual void setName(const String8& name);
+    virtual bool isVisible() const;
 
     // LayerBaseClient interface
     virtual wp<IBinder> getSurfaceTextureBinder() const;