media: Add InitializeWithUrl transport and URL player renderer

[abhijeetk]

Add mojom::Renderer::InitializeWithUrl(client, source_url) to deliver
the URL on the renderer Mojo pipe, keeping URL delivery and
initialization ordered on the same pipe.

Add UrlPlayerRenderer for tvOS URL-based playback via SbPlayerBridge
and UrlPlayerRendererWrapper as the Mojo service bridge. The wrapper's
InitializeWithUrl() sets the URL on the renderer internally then calls
Initialize().

MojoRendererService validates the renderer type and URL before
forwarding via static_cast, guarded by GetRendererType() == kUrlPlayer
and ReportBadMessage().

Bug: 512045535

[github-actions]

🤖 Gemini Suggested Commit Message

---

media: Add URL player renderer for tvOS

Introduce InitializeWithUrl to the mojom::Renderer interface and
implement UrlPlayerRenderer to support URL-based media playback.
This change is primarily targeted at tvOS to enable native HLS
playback via SbPlayerBridge.

By delivering the source URL directly on the renderer Mojo pipe,
delivery and initialization remain ordered. This also includes
the necessary Mojo service wrappers and build system flags to
enable this functionality for tvOS builds.

Bug: 512045535

---

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[gemini-code-assist]

Code Review

This pull request introduces UrlPlayerRenderer and its Mojo wrapper UrlPlayerRendererWrapper to support URL-based media playback on tvOS using Starboard. The code review feedback focuses on improving robustness, safety, and style guide compliance. Key recommendations include replacing unsafe CHECK and DCHECK statements with graceful runtime checks, initializing primitive local variables to prevent undefined behavior, adding defensive null checks for client_ and player_bridge_ to avoid crashes, and removing unused private member variables. Additionally, the reviewer notes that both new classes require detailed class comments explaining their lifetime, ownership, and threading models to adhere to the repository style guide.

[borongc]

Since url player is only on tvOS, just want to check if checking is_tvos is sufficient?

[abhijeetk]

Since url player is only on tvOS, just want to check if checking is_tvos is sufficient?

No, is_tvos alone isn't sufficient and doesn't exist as a standalone buildflag in the build system. tvOS is identified as is_ios && target_platform == "tvos".

use_starboard_url_player is defined as use_starboard_media && is_ios && target_platform == "tvos" in starboard/build/buildflags.gni. The use_starboard_media dependency is required because the URL player stack is built entirely on top of Starboard infrastructure. It uses SbPlayerBridge for player creation, StarboardRendererExtension/StarboardRendererClientExtension Mojo interfaces for SbWindow and video geometry, and SbDrmSystem for FairPlay DRM. Without use_starboard_media, none of these would be compiled in.

[abhijeetk]

cc : @jkim-julie @Gyuyoung @rakuco

[borongc]

Since url player is only on tvOS, just want to check if checking is_tvos is sufficient?

No, is_tvos alone isn't sufficient and doesn't exist as a standalone buildflag in the build system. tvOS is identified as is_ios && target_platform == "tvos".

use_starboard_url_player is defined as use_starboard_media && is_ios && target_platform == "tvos" in starboard/build/buildflags.gni. The use_starboard_media dependency is required because the URL player stack is built entirely on top of Starboard infrastructure. It uses SbPlayerBridge for player creation, StarboardRendererExtension/StarboardRendererClientExtension Mojo interfaces for SbWindow and video geometry, and SbDrmSystem for FairPlay DRM. Without use_starboard_media, none of these would be compiled in.

In this case, I think the gating logic should be like this:

if (use_starboard_media) {
  if (is_ios && target_platform == "tvos") {
    url_player code...
  }
}

Starboard should contain multiple platforms (android, tvOS, and 3P devices), so the flag use_starboard_url_player doesn't make sense to me, as it should be a subset of use_starboard_media as you define use_starboard_url_player as use_starboard_media && is_ios && target_platform == "tvos".

[abhijeetk]

Thanks for all review comments. We are moving ahead with approach in PR #10698 (UrlPlayer using StarboardRenderer).
Closing this PR.