QtQuick.Controls 2 ToolBar memory leak when resizing

There is a huge memory leak in the ToolBar from QtQuick.Controls2 when choosing Material theme.

How to reproduce:
Create an ApplicationWindow, put ToolBar into it's header, set Material theme in qtquickcontrols2.conf. Now launch your application and try to resize the window. Memory consumption will start to grow very fast.

I think this issue related only to Windows, because my colleague could not reproduce it on Linux.

UPDATE:
I have found that the actual problem is buggy DropShadow effect.
It is attached to the ToolBar when using Material theme, but setting Material.elevation to 0 fixes memory leak (but removes shadow effect).
Adding DropShadow effect to the scene manually also causes huge memory leak on window resize. See updated main.qml.