1. The output isn't great. It can be hard to find hotspots and, even
when you do find them, to find why those are hotspots.
2. It uses some jQuery-specific frontend code which we can remove now
that we don't have this any more.
3. It's only possible to profile the initial request, not any subsequent
AJAX requests.
This commits replaces `params` with `safe_params` in `url_for` helpers
to resolve security issues [1] and failing specs with the
```
ArgumentError:
Attempting to generate a URL from non-sanitized request parameters!
An attacker can inject malicious data into the generated URL, such as
changing the host. Whitelist and sanitize passed parameters to be secure.
```
error.
[1]: https://gitlab.com/gitlab-org/gitlab-ce/issues/45168
But first, rewrite the performance bar in Vue:
1. Remove the peek-host gem and replace it with existing code. This also allows
us to include the host in the JSON response, rather than in the page HTML.
2. Leave the line profiler parts as here-be-dragons: nicer would be a separate
endpoint for these, so we could use them on Ajax requests too.
3. The performance bar is too fiddly to rewrite right now, so apply the same
logic to that.
Then, add features! All requests made through Axios are able to be tracked. To
keep a lid on memory usage, only the first two requests for a given URL are
tracked, though. Each request that's tracked has the same data as the initial
page load, with the exception of the performance bar and the line profiler, as
explained above.
