feat(block): Chain ElementProbe parents; add to shadowRoot

[mhevery]

This allows one to retrieve ElementProbe from any element including
a shadowRoot. The ElementProbe contains element, injector, and scope.
The added benefit is that by waling the ElementProbe parent one can
get the parent element of a shadow DOM.

[mhevery]

@pavelgj @codelogic

[pavelgj]

Is this still meant as a debugging only feature? Jailbreaking Shadow DOM encapsulation seems dangerous if people start using this as a prod feature.

[codelogic]

No, its for optimization. Specifically in the case of animation we want to be able to find out if any animations are running on any parents. This is especially important during page loads and routing changes where an entire page could contain a large number of animations. In order to do this, we need to walk the dom and break out of the shadow root. Also, having a is version of an element is lighter to touch and for parent animation checks we may not even have to touch the Dom at all.

[codelogic]

Did you intend for this to also wrap an element probe around every directive (not just components)? I was tinkering around with the code for animation optimization after this went in and I couldn't rely on the element probe to reliably exist on every element I wanted to check.

[zoechi]

Isn't there a way to register animations centrally (like in a service) when they are started, and go through that list, instead of iterating the DOM?

[codelogic]

That would be awesome, but the problem is how do you know given Element "A" and Element "B" if "Element C" is a child somewhere down the chain of either A or B without doing a dom walk up the tree from C?