GitLab

Add the content description for the loading spinner so that the screen
reader can read out the loading status correctly.

Change-Id: Ifa46b4b1c2d8255a592751132d56f66edb8b1257
Bug: 1119587
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2368445
Commit-Queue: Wenyu Fu <wenyufu@chromium.org>
Reviewed-by: Sky Malice <skym@chromium.org>
Reviewed-by: Theresa  <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#805951}