Canvas3D and three.js does not work using QQuickWidget inside QMdiArea since 5.6

When running the Canvas3D and using the three.js API inside a QMdiArea using a QQuickWidget, it does not work anymore since 5.6 release, got the following debug messages
qrc:/three.js:34720: TypeError: Property 'resize' of object [object Object] is not a function
qml: Canvas3DRenderer: trying to use 0 texture units while this GPU supports only 0
qml: Canvas3DRenderer: trying to use 1 texture units while this GPU supports only 0
qml: Canvas3DRenderer: trying to use 2 texture units while this GPU supports only 0
qml: Canvas3DRenderer: trying to use 3 texture units while this GPU supports only 0
qrc:/three.js:34720: TypeError: Property 'resize' of object [object Object] is not a function

Repeated over and over again.
This works perfectly with Qt 5.5, something has happened since 5.6 release.

I attach a modified version of the "oneqt" example that reproduces this issue.
NOTE: I have only tested on Linux - Ubuntu 15.10 so far.