Show text message "Loading File attachments..." in the files placeholder while the attachments are loading

Review Request #8642 — Created Jan. 20, 2017 and submitted — Latest diff uploaded

Information

Review Board
master
c68def2...

Reviewers

When load a review request with some file attachments, the "Files" list appears blank until the attachments finally load in, it looks broken.
After change, a text message "Loading File attachments..." will show in the files placeholder while the attachments are loading.

I have made some testing as following:
1. Created a new review request (File attachment request only), then added a file, after clicking "UPLOAD" button and before a file is loaded, the text message is showing in the files placeholder. Once the file is uploaded, the text message is replaced by the file thumbnail.
2. For an existing request (File attachment request only), when I added a new file, same thing happened as above.