Fixes #2509: Fixed race condition when image didn't get transferred from report site issue extension

[ksy36]

r? @miketaylr

[wisniewskit]

Looks good to me. Worth having a second set of eyes on it though, in case our approach is disagreeable.

[wisniewskit]

Mike, could you take a look at this as well? This change looks hefty, but if you look at the individual commits, it's not really that evil. The first commit is just us unindenting functions and putting them on the prototype of Bugform (so that they are created when the page loads, not after jQuery.ready).

The second commit is the actual interesting change, where we just change how the constructor of BugForm works so that it calls jQuery.ready at appropriate times, so the message-listener is added right away, but it only actually handles the message after jQuery.ready.

[miketaylr]

Yep, this looks good. Reviewing each commit is less scary. :)

[karlcow]

Thanks a lot @ksy36 and @wisniewskit !!!

[karlcow]

I'll deploy this next week.