This introduces an ArrayBuffer front, so that we no longer need to go through the thread client to get an array buffer for the sourceFront (this is the only place it is used).
It also converts the arrayBufferActor to a protocol.js actor. I was running into an issue between them. I need to double check what this issue was. If these two refactors need to be split, I can do that, but for now it looks like it wasn’t that large of a change.
Differential Revision: https://phabricator.services.mozilla.com/D27878
Alexandre Poirot