PointerEvents registration fails in the presence of ShadowDOMPolyfill in some cases

[sorvell]

Under ShadowDOMPolyfill, the back button in projects/youtube does not function when on-tap is used to trigger it.

PointerEvents monitors dom via mutation observers. It installs listeners on document and on each shadowDOM toolkit creates.

For the g-toolbar containing the back button, PointerEvents sees the node being removed from dom and unsets its touch-action. This makes the tap event non-functional. This is unexpected since the g-toolbar is not removed from dom.

A quick test shows that if we avoid installing the PointerEvents mutation observer on shadowRoots, the problem goes away. This is unexpected since the node is not removed from the shadowRoot.

[dfreedm]

Addressed in toolkitchen/PointerEvents#56