[web-animations] Naming of timing groups in the API

Hi,

A number of people have expressed concern about the names "ParGroup" and 
"SeqGroup" used in the Web Animations API for parallel timing groups and 
sequence timing groups so we are looking for better names.

Some considerations:

* It should be short--experience tells us authors hate typing long names 
and these are two interfaces we expect authors to type a lot.

* It shouldn't clash with usage in existing libraries.

* Within the spec we've used "animation" in a narrow sense to mean 
"actually applying an effect to a target element over time". So we have 
"timed items" but only timed items that actually apply an effect, e.g. 
interpolate a property value, are called "animations". The reasoning is 
that if you have some groups that sequence a series of videos and audio 
clips, do you really call that animation? It also matches the 
distinction we make between the timing model and animation model but 
feel free to question this naming.

Some ideas thrown around so far:

* Sequence and Parallel (might risk clashes? What is a "Parallel", it's 
not a noun so "new Parallel" is weird)
* Sequence and Group (we'd have to call the superclass something else, 
but, who cares--no one ever types that)
* TimingSequence and TimingGroup (unlikely to clash but long)
* TimingSequence and TimingSet ?
* AnimationSequence and AnimationGroup (conflicts with our narrow use of 
the term "animation")
* Sequence and Timeline (and rename our existing "timeline" to "clock", 
e.g. document.clock.play(...) -- a bit weird?)
* Sequence and Together
* ???

And while we're on the topic, there are a number of other interfaces 
where concern has been expressed about them possibly clashing:

* Player
* Timing
* Timeline

(Although note that none of these have constructors so authors won't 
currently be typing them meaning it's probably fine if they're longer.)

Any thoughts welcome! We'll probably rename everything at LC anyway ;)

Best regards,

Brian