Export createItems call to enable plugins to hook into process

[dominic-p]

The pull request is more of a request for feedback. This seems like the path of least resistance to enable plugins to add menu buttons (see #648), but it's entirely possible that I've missed something obvious (sorry if that's the case).

[heff]

Cool, good idea. I would instead export that here:
https://github.com/videojs/video.js/blob/v4.1.0/src/js/exports.js#L92

goog.exportProperty(vjs.MenuButton.prototype, 'createItems', vjs.MenuButton.prototype.createItems);

And then use a string key anywhere createItems is called

this.items = this['createItems']();

If you want to update that and make sure it works, I'll pull it in.

[dominic-p]

Ok, the changes have been made. My fork got a little messed up, so I had to get rid of the original commit and start over. I've tested it in my environment, and it seems to be working as expected. Let me know if anything looks amiss to you.

[heff]

Ah, you actually don't need the last three string key updates, vjs.MenuButton.prototype['createItems'] and both in tracks.js. In fact that will probably break those functions. Sorry, that was totally my fault.

[dominic-p]

Ok, I rolled back the unnecessary conversions. Not your fault at all. I'm still trying to wrap my head around Closure's advanced compilation.

[heff]

Ok wow, this is frustrating. It looks like those other items need to be exported too in order to work. Instead though, add these lines after the first exportProperty you did in exports.js.

goog.exportProperty(vjs.TextTrackButton.prototype, 'createItems', vjs.TextTrackButton.prototype.createItems);
goog.exportProperty(vjs.ChaptersButton.prototype, 'createItems', vjs.ChaptersButton.prototype.createItems);

Sorry for the runaround. Closure compiler can be frustrating, but it makes things so dang small. I actually hoping to dig into a new minifier project called esmangle in the future.

[dominic-p]

Alright, I think that does it. Sorry about the stupid extra file that showed in the last set of commits. I don't think it should effect anything, but let me know if you would like me to wipe all of these commits clean and push a single commit with everything.

[heff]

Awesome, thanks! I can clean up the commits with Pulley.