Support for {{binding.events.via.a.path}}

[nevir]

Primarily, this allows for JS-less event wireup, such as:

<polymer-element name="x-foo">
  <template>
    <core-overlay id="overlay"></core-overlay>
    <button id="button" on-tap="{{$.overlay.toggle}}"></button>
  </template>
</polymer-element>

Also, I snuck in a warning (when logging is on) to help diagnose when method dispatch fails to resolve

[nevir]

Doh, I totally missed #19 & associated commit - but I think this satisfies it?

[sjmiles]

This is more of a conceptual issue at the moment than a code issue; iow, there is some debate over the proper syntax and layering for event mapping.

Wrt to this particular patch, there are already functions that do efficient object-path resolution, so we probably do not want to re-implement that in dispatchMethod without a solid rationale.

[nevir]

Makes sense on the conceptual front; definitely a bit awkward as-is.

Re: the object/path resolution helper - I poked around the polymer repo for a while, but was unable to find any. Have any tips on where they might be hiding?

I guess what I really want is a variant of Path#getValueFrom that also returns the implied receiver (e.g. whatever object the second to last path component resolves into) - or just handles the method dispatch for me.

Maybe a MemberMethodPath (or whatever name) specialization is a good route? Or another method on Path.

[sorvell]

I also want to support this:

<button id="button" on-tap="{{$.overlay.toggle}}"></button>

but I think our approach needs to be a bit deeper since I think it'd also be good to support this at the same time:

<template repeat="{{user in users}}">
  <button id="button" on-tap="{{user.add}}">Add</button>
  ...