Comment 13 for bug 1522638

After further use and testing (integrating with other branches), I have added another feature to the progress dialog: a semi-determinate mode. With this, the <progress/> bar appears as an indeterminate bar (showing no specific indication of progress), but the dialog also shows the current value (assuming it's set).

This is useful when we know how many of something we have retrieved from the server, but we have no way to know how many we will ultimately retrieve. (This is a surprisingly common scenario, because it's faster to simply fetch stuff than to first ask how many stuff's I'll be getting). This allows us to show that actual progress is being made, without creating an imaginary end-point for the progress.

Will push the new commit shortly for another set of eyes.