HTMLImports.Loader maybe callback twice

[niuhf0452]

I apologize for my bad english first.
When I write x-page (an element to load html file into main document dynamically, like iframe),
I use this method:

 HTMLImports.importer.load(doc, myCallback);

Sometimes, myCallback will be called twice.
In HTMLImports/src/Loader.js, I found the call sequence:
addNodes -> require -> dedupe -> tail -> checkDone,
and
addNodes -> checkDone.
If all the 'nodes' to fetch are cached before, then oncomplete will be called twice. And it indeed called twice sometime.
It seems there's no matter with HTMLImports/src/Parser.js, but it really bother me.

[dfreedm]

Marking this WONTFIX.
We are removing this hacky loader api for the ability to watch for new <link rel="import"> elements inserted dynamically, the same as what you would do in a native browser implementation of HTML Imports.

This new ability will be enabled in the next release.

Mailing list thread with a similar question: https://groups.google.com/forum/#!msg/polymer-dev/pn1mhqLugVU/iQnfaH4W5_sJ