Youtube playback and decoding issue

[cocobean]

WebPositive does not accurately render the Youtube video controls and no longer does Youtube video/audio (MP4 (H.264/AAC), WebM (vp8/vp9)) playback. Non Youtube video/audio playback happened after R1B2 release (videos still work in other browsers).

[cocobean]

WebCore MediaPlayerPrivate build issue

[cocobean]

haikuwebkit-1.7.1-1 reproduced the 'supported media formats' build issue on hrev54662. Issue with GCC 8.3.0 unique_ptr usage from MediaPlayerPrivateHaiku.cpp.

[pulkomandy]

It seems Youtube has dropped support for using normal html5 <video> tag and instead uses media source extensions.

​https://developer.mozilla.org/en-US/docs/Web/API/Media_Source_Extensions_API

The original idea of <video> is that the website would just give the URL to a media file, and the web browser would handle playing it (leaving us with the responsibility of buffering the data, handling seeking, etc).

MSE moves a lot of this into javascript code of the website. Which means it is no more a simple wiring of WebKit with the media kit.

Currently MSE is disabled in our builds of WebKit. They should be enabled (turn ​https://github.com/haiku/webkit/blob/rebased/Source/cmake/OptionsHaiku.cmake#L82 to ON) and then fixed so that they actually work (I think I had the code building at some point, but it was not working, so we had disabled it to revert to the basic video support, which, at the time, was working better)