[webkit-gtk] how did the video frame shared between "webkitwebprocess" and "waylandcompositer"

[tugouxp]

HI folks:
     
   it seems the video frame data processed by the "webkitwebprocess" gstreamer staff need to be send to  UI process for compositor  and display, 
 the UIprocess has a nested compositor called "wl_webkitgtk" to do this.
but when i tracing the flow, i did not find the way that share the video frame buffer between two process,  no hint about "shm" and "socket" mechanism, 


so, how the data be shared? need do a copy  operation for share?


thanks for your help!
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