* globalToLocal was just broken when there was a rotation and a
translation at the same time. This fixes that and adds a test.
* update graphic used by spinning_mixed since the old one went 404.
* simplify some of the code in the demo.
* fix MatrixUtils.transformPoint to be consistent with how we transform
points elsewhere.
* stop transforming points elsewhere, just use
MatrixUtils.transformPoint.
* make the Widget binding handle not having a root element.
* make the spinning_mixed demo update its widget tree.
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