We landed a student project for displaying desktop notifications in

Review Board 3.0, but unfortunately the final revision did not work.

There were a handful of problems, starting with bad variable references

that simply prevented the browser from prompting for permission to

display notifications and prevented those notifications from ever being

displayed. There were other issues as well, such as hard-coded strings,

lack of click support for notifications, and no body text.
This fixes up the support to properly work. Now, users will be prompted

for permission when next viewing the review request page, and if

granted, a notification will be shown whenever the in-page updates

bubble would be displayed.
We are limited in what we can show in that bubble, in terms of the

structure and length of content. For now, the summary of the

notification matches the summary from the API ("Review request updated",

"Diff updated", "New review", etc.). The body then contains the review

request ID and the person who made the update. This isn't perfect, but

even as-is, the name gets cut off on macOS. Other platforms may impose

their own limitations as well.
Still, it's useful when not paying attention to the page. Going forward,

we may want to tweak the content for the notification (perhaps adding

more information in the API that we can use), and perhaps add action

support for things like viewing the diff, for platforms that support it.

Tested that notifications worked on Chrome and Firefox. I was prompted

when visiting the page, and then shown notifications any time the

updates bubble appeared.
Tested that clicking the notification reloaded the review request page.