Rename Distributed Nodes Algorithm to Slot Assignment Algorithm

[rniwa]

Like the issue #322, we should just get rid of the term "distribution" everywhere in the spec. It's unwarranted use of a historical jargon that doesn't merit anyone.

[hayatoito]

One web-exposed API which is using the term "distribution" is slot.getDistributedNodes().

http://w3c.github.io/webcomponents/spec/shadow/#widl-HTMLSlotElement-getDistributedNodes-sequence-Node

We need to rename this. How about slot.getComposedNodes()?

Regarding with other usage of the term "distribution" in the spec, we do not have to be in a hurry. We can fix that later.

[rniwa]

Now about getAssignedNodes() with a boolean argument specifying deep/flatten?

[hayatoito]

I'm fine with getAssignedNodes() with a boolean parameter:

    sequence<Node> getAssignedNodes(optional boolean deep/flatten/oranythingelse);

sequence<Node> could be FrozenArray[Node], that is another issue.

[annevk]

Please no boolean parameter. Use a dictionary with a single member that defaults to false. We always find out over time we wanted more parameters. And it's better that boolean parameters are named.

[hayatoito]

+1. Let's use a dictionary even when only one parameter is expected, as of now.

[TakayoshiKochi]

As commented in #361 (comment)
deepPath is for #361.