Cherry pick PR #8962: cobalt: Move VideoGeometrySetterService on gpu thread

[cobalt-github-releaser-bot]

Refer to the original PR: #8962

Relocate the VideoGeometrySetterService from the browser process to
the GPU process. This change instantiates the service within the
CobaltContentGpuClient, allowing it to be managed directly on the GPU
thread.

This improves performance and reduces IPC overhead for video geometry
updates by co-locating the service closer to the GPU and compositing
operations. The StarboardRendererWrapper now directly subscribes to
video geometry changes from this local service.

Mojo communications:

• Before: viz (gpu) --> browser thread --> StarboardRendererClient (media) --> StarboardRendererWrapper (gpu)
• After: viz (gpu) --> StarboardRendererWrapper (gpu)

Note this is called nearly per UI frame update.

Issue: 405424096

[cobalt-github-releaser-bot]

Caution

There were merge conflicts while cherry picking! Check out cherry-pick-26.eap-8962 and fix the conflicts before proceeding. Check the log at https://github.com/youtube/cobalt/actions/runs/22469573981 for details.

[github-actions]

🤖 Gemini Suggested Commit Message

---

cobalt: Move VideoGeometrySetterService to GPU thread

Relocate the VideoGeometrySetterService from the browser process to
the GPU process. This instantiates the service within the
CobaltContentGpuClient, allowing it to be managed directly on the GPU
thread.

This improves performance and reduces IPC overhead for video geometry
updates by co-locating the service closer to GPU and compositing
operations. The StarboardRendererWrapper now directly subscribes to
video geometry changes from this local service, eliminating
intermediate IPC hops through the browser process.

Bug: 405424096

---

💡 Pro Tips for a Better Commit Message:

1. Influence the Result: Want to change the output? You can write custom prompts or instructions directly in the Pull Request description. The model uses that text to generate the message.
2. Re-run the Generator: Post a comment with: /generate-commit-message