[MSE][GStreamer] Support Google Dynamic Ad Insertion (DAI)

[philn]

296d132

[MSE][GStreamer] Support Google Dynamic Ad Insertion (DAI)
https://bugs.webkit.org/show_bug.cgi?id=216039
<rdar://problem/68638316 >

Patch by Philippe Normand <philn@igalia.com > on 2022-05-25
Reviewed by Alicia Boya Garcia.

The "simple DAI" demo was not working as expected because the new source pad of the demuxer in the append
pipeline was sinking buffers to a "black hole". That was happening because the second time the
no-more-pads signal was emitted, the previous source pad was still linked to a track, and there was
no code to unlink/relink demuxer pads. This is now handled...

The specific "simple DAI" demo generates 2 AAC streams, with different tkhd track-id fields, we had
no layout test reproducing this use-case, so this patch provides one.

Test: media-source/media-source-audio-track-id-switch.html

* LayoutTests/media/media-source/content/test-48kHz-new-track-id.m4a: Added.
* LayoutTests/media/media-source/content/test-48khz-new-track-id-manifest.json: Added.
* LayoutTests/media/media-source/media-source-audio-track-id-switch-expected.txt: Added.
* LayoutTests/media/media-source/media-source-audio-track-id-switch.html: Added.
* Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.cpp:
(WebCore::AppendPipeline::handleErrorSyncMessage):
(WebCore::AppendPipeline::didReceiveInitializationSegment):
(WebCore::createOptionalParserForFormat):
(WebCore::AppendPipeline::recycleTrackForPad):
(WebCore::AppendPipeline::linkPadWithTrack):
(WebCore::AppendPipeline::tryMatchPadToExistingTrack): Deleted.
* Source/WebCore/platform/graphics/gstreamer/mse/AppendPipeline.h:
(WebCore::AppendPipeline::Track::isLinked const):

Canonical link: https://commits.webkit.org/250950@main
git-svn-id: https://svn.webkit.org/repository/webkit/trunk@294791 268f45cc-cd09-0410-ab3c-d52691b4dbfc

[ntrrgc]

LGTM.

[webkit-early-warning-system]

Committed r294791 (250950@main): https://commits.webkit.org/250950@main

Reviewed commits have been landed. Closing PR #893 and removing active labels.