Let's try sending preconnect requests via mojo directly to the browser process from the BG parser thread for cross site preloads.

This will avoid the delay induced by the main thread which is often busy doing work for tens to hundreds of milliseconds.

In mojo, this can be done by creating a pipe on the BG parser thread, and passing its handle to the main thread to connect via its service registry. Subsequent calls through the pipe will go directly to the browser process.