Origins-based view for better Fission support

[gregtatum]

edit: I'm re-purposing this issue, as it has lots of good historical information and discussion. Before it was a discussion and meta bug. Now it's about improving and creating an origins based view. I landed PR #2513 which has an experimental approach for it. This needs to be cleaned up for correctness, and UI.

https://share.firefox.dev/2GDYUcb

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Original issue:

https://perfht.ml/2QTNnsn

This is not very nice, as can be seen from this screenshot:

┆Issue is synchronized with this Jira Task

[gregtatum]

First off, we create lots and lots of tracks. These can tell us useful information, but when there are so many processes it's probably not very handy. A quick fix could be to by default collapse to only the global tracks, and then provide an arrow to expand all of the local tracks underneath.

Perfetto does something similar:

Default to "collapsed"

Then click to expand:

[gregtatum]

We could reduce the amount of tracks by nesting the processes based on the main process for a page, and then dive into the processes that were launched by that tab.

v Parent Process
 - Network
 - Memory
 - Compositor
v Active Tab (1/2)
  - Network
  - Memory
  - Compositor
  - DOM Worker
  > IFrame Process (1/3)
  > IFrame Process (2/3)
  > IFrame Process (3/3)
> Active Tab (2/2)

[canova]

Breakdown of work we need to do(please edit and add more if you think we should):

• Land the MVP of "active tab view": Add "show active tab only" option #2335
• Land the presets and the new recording workflow(so we can have the preset information to know if the user is using "Web Developer" preset or not)
• Get the preset information from the profile data and change the view depending on that.
• Get a UI from the UX people.
• Break down the new UI to smaller pieces and implement the new UI that simplifies the single tab profiling(can be broken down more once we have the UI)

[julienw]

As a feedback from my Culture of Performance interview, we found it's difficult to find the right tracks for specific origins.

While I see value to the logic here, I wonder if we can have something simpler for now.

Strawman:

• have a select box with all found "pages" at the top of the page (similar to what we have in the devtools panel)
  • they could be nested like Greg did in the Origins view
• when selecting an entry, we would filter all tracks, without otherwise merging, and then feed the result to the auto-track-hiding algorithm

The advantage of this is that we probably have all the bits to do this already.

Greg's origins implementation still have additional value, in that it provides a cleaner view on all the tracks, but I believe this would benefit to less users in the end.

Thoughts?