Media Modal: the progress bar for each attachment no longer shows upload progress

[gcorne]

The progress bars in the attachment browser no longer animate when uploading. See ​https://cloudup.com/cAGpTEdfq6A for a demonstration. The progress bars worked correctly in 3.9.2.

This broke in [29266] because rerenderOnModelChange is set to true so any change triggers the view to re-render. The upload progress isn't handled during a normal Attachment view render, so always re-rendering causes any change to the progress bar to be overwritten.

[gcorne]

Actually, it looks like the binding of render to change happened in [28993].

[gcorne]

29367-01.patch​ fixes the issue by incorporating the percentage of progress into the template that is used to render. So when the change event is firing a re-render, the current percentage is reflected in the width of the progress bar. I handled it this way instead of calling this.progress() after this.$el.html() so that the progress bar wouldn't flicker.

[azaozz]

In 29609:

Media modal: fix the progress bar in the attachment thumbnail. Props gcorne, fixes #29367