pub fn initialize_worker()Expand description
Makes the worker of the calling thread take the canvases that are
transferred to it: installs the message handler of the registry of the
thread’s script, which creates the render target of each canvas and
reports it
(on_render_target_registered).
Called once, by a thread other than the one of the page, before a canvas is created with its id. The thread has to stay alive afterwards and return to the event loop of its worker, where the messages arrive.