Bug 265718 – [GPUP] Remove TrackPrivateRemoteIdentifier, fix memory leak

• Status: RESOLVED
• Resolution: FIXED
• Component: Media

[Jean-Yves Avenard [:jya]]

following bug 254099; we are no longer using AtomString as track identifier and as such we no longer need the `TrackPrivateRemoteIdentifier` to bridge the TrackPrivate living in the GPU Process to those in the web content process, instead simply using their TrackID (an uint64_t).

While in the process of performing this task, I identify a leak in the `MediaPlayerPrivateRemote` code, which was only partially fixed in bug 242925

Whenever a new init segment is parsed by a sourceBuffer in the GPU Process (through the SourceBufferParser); a new TrackPrivate is created and stored in the `InitializationSegment`

When the SourceBufferPrivate call the SourceBufferPrivateClient, the `RemoteSourceBufferProxy` will create a new `RemoteVideoTrackProxy` [1]
This is done by `RemoteMediaPlayerProxy::addRemote[Video|Audio|Text]TrackProxy`, which will check of the track id is already existing, and if so will overwrite it with the new TrackPrivate [2]
But regardless of the preview tack id, a `Remote[Video|Audio|Text]TrackProxy` will be created, with a new, unique TrackPrivateRemoteIdentifier [3] which will then create the RemoteVideoTrack/RemoteAudioTrack/RemoteTextTrack in the content process [4]
The code there ensure that the existing RemoteTrack with this unique TrackPrivateRemoteIdentifier doesn't exist and will create a new one.

This RemoteTrack will never be deleted, it just becomes unused as the corresponding TrackPrivate in the GPU Process got deleted.

[1] https://searchfox.org/wubkat/rev/02b2f8b7a253140d82f59e38a68257431139d2e7/Source/WebKit/GPUProcess/media/RemoteSourceBufferProxy.cpp#88,97,106
[2] https://searchfox.org/wubkat/rev/02b2f8b7a253140d82f59e38a68257431139d2e7/Source/WebKit/GPUProcess/media/RemoteMediaPlayerProxy.cpp#637-643
[3] https://searchfox.org/wubkat/rev/02b2f8b7a253140d82f59e38a68257431139d2e7/Source/WebKit/GPUProcess/media/RemoteMediaPlayerProxy.cpp#645-647
[4] https://searchfox.org/wubkat/rev/02b2f8b7a253140d82f59e38a68257431139d2e7/Source/WebKit/WebProcess/GPU/media/MediaPlayerPrivateRemote.cpp#762-764

[Jean-Yves Avenard [:jya]]

[press saved to quickly] bug 242925 identify the issue, but all it did was removed the TrackPrivate from the GPU process, not the corresponding TrackPrivateRemote in the content process.

[Radar WebKit Bug Importer]

<rdar://problem/119070875>

[Jean-Yves Avenard [:jya]]

Pull request: https://github.com/WebKit/WebKit/pull/21207

[EWS]

Committed 271599@main (e0a0bc967262): <https://commits.webkit.org/271599@main>

Reviewed commits have been landed. Closing PR #21207 and removing active labels.