New rich editing roadmap position paper

Hi, after I was involved in the IME event level debate, I was asked to
formulate my opinion on where I think things should evolve instead, based
on my experience with Android IME.  Here is my position paper on that,
which I've already passed around to other Chromium-team members and
incorporated their feedback:

https://docs.google.com/document/d/10qltJUVg1-Rlnbjc6RH8WnngpJptMEj-tyrvIZBPSfY/edit

It's a new approach involving hidden textareas which I believe avoids the
pitfalls of previous variants of that idea.  More importantly, each of the
individual standardization items should be small, uncontroversial and
compatible with other visions -- because I don't expect or want to force
everyone to hidden textareas.  Basically, it's a way of framing small
practical subprojects in a way that they appear as incremental steps
towards eventually enabling a full Office-style text editor.

One more note: I'll be leaving Chromium-team at the end of this month so I
unfortunately won't be able to defend the position at TPAC.  Chromium-team
editing folks have mostly been positive about this roadmap, but are still
overall debating how and how much to invest in editing, so I'm putting this
paper out there as a starting point for future discussion that I won't be
involved in.