Creating XMLHttpRequest in sandbox throws error

[poke]

When calling new XMLHttpRequest from within a sandbox plugin, the following exception is raised:

Error: [Exception... "Failure"
    nsresult: "0x80004005 (NS_ERROR_FAILURE)"
    location: "JS frame :: resource://dtaac/sandboxfactories.jsm :: XMLHttpRequest_WRAP :: line 55"
    data: no]
Source File: resource://dtaac/sandboxfactories.jsm
Line: 55

The line in question is within the constructor of the wrapped XHR, where the inner XHR object is instantiated. Apparently the constructor throws an exception:

this._xhr = new XMLHttpRequest();

I tried to figure out why it happens, but I’m a bit lost now. The constructor XMLHttpRequest itself is available; and many related problems on the web with that error code say it’s cross-site-related, but by the time the line gets executed there’s no information about any URL yet.

[nmaier]

Are you on Nightly by chance?

[nmaier]

Nightly bug: https://bugzilla.mozilla.org/show_bug.cgi?id=741367

[poke]

Good catch! I keep forgetting that I should expect such issues in Nightly (it works so well most of the time ^^). Guess I should install Aurora for testing as well.

[nmaier]

I had stumbled upon this problem in other extensions and already had a TODO to find an existing bug or otherwise track down the culprit and file one myself. Actually quite a few extensions are affected :p Closing this issue now as I expect this will be fixed in m-c directly. In the unlikely case the bug makes it into m-a, then we may re-evaluate that decision.

[poke]

Just a quick note: It works perfectly in Aurora, and after fixing the plugin a bit more, that works perfect as well ;)