ui: Add defaultPlugins to Embedder interface

[dreveman]

Allow embedders to control which plugins are enabled by default by
adding a required defaultPlugins property to the Embedder interface.
Both existing embedders return the built-in default list, preserving
current behavior while letting third-party embedders customize it.

Move default_plugins.ts into the embedder folder and pass the
default plugin list to PluginManagerImpl via the constructor.

[dreveman]

It would be nice to keep this in the embedder implementation instead of having to modify the default list. But maybe there's a way to do this already that I missed?

[github-actions]

🎨 Perfetto UI Builds

• 2578abb (2026-03-30 18:30 UTC): https://storage.googleapis.com/perfetto-ci-artifacts/gh-23760888567-1-ui/ui/index.html
• 680d563 (2026-03-30 19:27 UTC): https://storage.googleapis.com/perfetto-ci-artifacts/gh-23763352490-1-ui/ui/index.html
• b88072b (2026-03-30 20:43 UTC): https://storage.googleapis.com/perfetto-ci-artifacts/gh-23766654268-1-ui/ui/index.html
• 2a09fcc (2026-03-30 21:34 UTC): https://storage.googleapis.com/perfetto-ci-artifacts/gh-23768711064-1-ui/ui/index.html

[LalitMaganti]

Wouldn't it be far better to just move the default plugin list to the embedder interface? That seems like a no-brainer instead of adding a lambda for this.

[dreveman]

Wouldn't it be far better to just move the default plugin list to the embedder interface? That seems like a no-brainer instead of adding a lambda for this.

I would like to avoid having the embedder be aware of all default plugins. Eg. the change we made to move some gpu related code from TPTrack plugin to a new Gpu plugin shouldn't require all downstream embedders to update their code. But maybe you're suggesting moving into the embedder in a way that would allow this?

[LalitMaganti]

I mean ultimately in my mind how the embedder chooses to modify the embedded list is an implementation detail. You are free to depend on the upstream embedded definition and modify it or wholesale replace it.

I just don't think the API should be a lambda, that just feel weird to me.

[dreveman]

I mean ultimately in my mind how the embedder chooses to modify the embedded list is an implementation detail. You are free to depend on the upstream embedded definition and modify it or wholesale replace it.

I just don't think the API should be a lambda, that just feel weird to me.

Ah, done. Ptal.

[LalitMaganti]

Looks good to me but will leave to Steve to confirm he's happy.

[dreveman]

Looks good to me but will leave to Steve to confirm he's happy.

@stevegolton Let me know how this looks to you.