No way to set progress callbacks for xhr.upload when using dojo/request/xhr

[ddumont]

​https://bugs.dojotoolkit.org/ticket/13375 mentioned that this support was in dojo/request/xhr but I took a look at the code today and found no way to add a progress callback to the xhr.upload object.

[dylan]

I will look into this for 1.12, though would of course review a pull request if one is provided sooner.

Basic workflow would be:

• Hook it up to the separate upload handler
• See the response handler, its third argument, has an xhr object (backcompat handler), from there you can get the xhr and measure its progress.
• request.get(url, options, true) -> returns a deferred instead of a promise when the third param is set to true