Implement typeahead suggestions on the subreddit field of the submit form

[Kerrick]

Right now the subreddit box is static, which works if you know the subreddit name you want to submit to. However, implementing a typeahead dropdown would be nice, because it would act more like the form at http://www.reddit.com/submit does.

[Kerrick]

Should I poll http://www.reddit.com/api/search_reddit_names.json or sholud I maintain a list of the X most popular subreddits? The former would give a larger breadth of suggestions, but might seem slower for Mostly Harmless users, and might unnecessarily tax the Reddit API.

/cc @chromakode

[chromakode]

The search_reddit_names API endpoint was created expressly for completing subreddits on the submit page. As long as you abide by the API usage guidelines, I don't think it should impact us more than a regular submit page.

[Kerrick]

I'm going to call this blocked on code.google.com/chromium#20226, because I'd rather implement it using the native HTML5 <datalist> element.

[Kerrick]

Apparently, Chrome now supports the <datalist> element. Removing external dependency block.