starboard: Refactor FakeGraphicsContextProvider to use JobThread

[kjyoun]

This change replaces the manual pthread and functor queue logic in FakeGraphicsContextProvider with JobThread. This simplifies the threading and synchronization logic, making it more robust and maintainable.

To support this, JobThread and JobQueue have been moved into a dedicated source_set in //starboard/shared/starboard/player:job_thread, allowing them to be shared across the platform implementation and tests without duplicate symbol issues. All relevant platform and test targets have been updated to depend on this new target.

Bug: 468356861

[kjyoun]

/gemini reviw

[github-actions]

🤖 Gemini Suggested Commit Message

---

starboard: Refactor FakeGraphicsContextProvider to use JobThread

This change replaces the manual pthread and functor queue logic in
FakeGraphicsContextProvider with the JobThread utility. This simplifies
the threading and synchronization, improving robustness and
maintainability.

To support this, JobThread and JobQueue are moved to a dedicated
source set at starboard/shared/starboard/player:job_thread. This
allows sharing the utility across various platform implementations
and tests without symbol conflicts. All relevant targets now depend
on this new source set.

Bug: 468356861

---

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[kjyoun]

/gemini review

[gemini-code-assist]

Hi kjyoun,

Thanks for requesting a review! I've analyzed the changes in this pull request.

This refactoring to use JobThread in FakeGraphicsContextProvider is a significant improvement. It successfully simplifies the threading and synchronization logic, making the code much more robust and maintainable. The move of JobThread and JobQueue to a dedicated shared source set also enhances modularity and reusability across the project.

Here's a summary of my findings:

• Correctness: The replacement of manual pthread and functor_queue mechanisms with JobThread is logically sound and should lead to more reliable threading. The use of ScheduleAndWait and BelongsToCurrentThread() ensures proper synchronization and avoids common threading pitfalls.
• Efficiency: Centralizing thread management with JobThread is generally more efficient than ad-hoc pthread and mutex/condition_variable implementations, as it can optimize resource usage and reduce overhead.
• Maintainability: This is where the biggest gains are. The code in fake_graphics_context_provider.cc is now much cleaner and easier to understand. Removing the boilerplate for thread creation, joining, and explicit synchronization greatly improves readability and reduces the cognitive load for future developers.
• Security: By simplifying complex threading logic, the risk of introducing race conditions or deadlocks is reduced, which indirectly contributes to a more secure and stable codebase.

Overall, this is a well-executed change that aligns perfectly with the pull request's description. Great job!

If you have any further questions, feel free to ask.

[gemini-code-assist]

Code Review

This pull request refactors FakeGraphicsContextProvider to use JobThread, replacing manual pthread and queue management. This is an excellent change that significantly simplifies the threading logic, making the code more readable, robust, and maintainable. The related changes to move JobThread and JobQueue into a separate source_set and update all dependencies are also well-executed. I have one minor suggestion regarding GN style for file paths to improve adherence to the Chromium style guide.