Send timestamp with initial request.

[jcblw]

I am doing some performance work, and my brain got thinking around how the messages panel works in the dev tools. Currently, the timing is based.

Messaged received in background -> message response sent.

It would be nice to be able to potentially see any IPC time even though it should be tiny. It would be interesting to be able to get a more full timing of messaging especially if there are potential issues with the background process that is making it not accept connections right away. So now timing would be.

Message sent -> Messaged received in background -> message response sent.

Message sent to message received would represent time spent in IPC.