[x-repeat] can't bind to childNodes under Shadow DOM

[justinfagnani]

With a template like this:

<template>
  <template is="x-repeat" items="{{fooNodes}}">{{item.nodeName}}</template>
</template>

And code like this:

this.fooNodes = Polymer.dom(foo).childNodes;

An exception is thrown under Shadow DOM, but not Shady DOM:

Uncaught TypeError: this.collection.observe is not a function

[justinfagnani]

I presume this is because Polymer.dom().childNodes is an Array under Shady DOM, but a NodeList under Shadow DOM.

If possible, x-repeat should be made to handle NodeLists, if not Polymer.dom() should tag its arrays somehow so that they also cause an exception in x-repeat.

[sorvell]

Currently x-repeat requires an array. We should probably make Polymer.dom().childNodes an actual array for consistency, but it does cover up a potentially confusing issue wrt x-repeat.

[justinfagnani]

Making childNodes an Array would be nice for consistency...