Viewing the pipelines tab on an MR leads to a dramatic increase in memory usage

If I visit this MR (which is just an example of a 'medium' sized MR with a 'medium' number of pipelines) and load the Overview and Changes tabs, Firefox reports around ~130 MB of memory used: !49243 (merged) That's not great, but OK.

Once I visit the Pipelines tab, memory usage doubles. Not only that, overall browser performance suffers: sometimes my browser hangs entirely for a while. The pipelines.json response itself from the server is over a megabyte (and very slow), which probably doesn't help.

Here's a memory snapshot from Firefox:

(It's just a screenshot as I'm not sure how best to share the actual snaphost, which is ~40 MB.)

Here's the FPS counter from a profile spanning the loading of that tab. Note that FPS drops to zero for several seconds:

I can upload the profile as it's much smaller: profile.json