>>106208484
That's really hard to say.
I don't know shit about chrome so I'll try to give an example from what I know of firefox.
Firefox uses its own message-passing, actor model library for dealing with IPC shit.
https://firefox-source-docs.mozilla.org/ipc/ipdl.html
IPC is used in a several places, like DOM level, gecko processes, GPU observer, async I/O and a lot more places. Content process are well sandboxed and subdivided into types based on what features each content process is supposed to have. How the IPDL serializes and passes the message over is another complex topic. Finding if IPDL is using pipes or shared memory under the hood is difficult through documentation. Looking through source code is the best way to get certain about it.