Add layered buffer support to libui and libgui.

Bug: 31686534
Test: manual
Change-Id: Ia40270701467f4b785660324cad883e7da08989a
diff --git a/include/ui/GrallocMapper.h b/include/ui/GrallocMapper.h
index 5517449..868fd14 100644
--- a/include/ui/GrallocMapper.h
+++ b/include/ui/GrallocMapper.h
@@ -63,6 +63,11 @@
         return mMapper->getFormat(mDevice, handle, &format);
     }
 
+    Error getLayerCount(buffer_handle_t handle, uint32_t& layerCount) const
+    {
+        return mMapper->getLayerCount(mDevice, handle, &layerCount);
+    }
+
     Error getProducerUsageMask(buffer_handle_t handle,
             uint64_t& usageMask) const
     {