[DevTools] Send DevTools request ID through URLLoader

Sending the DevTools request ID through the URLLoader interface allows
us to emit DevTools events from the browser process which refer to
specific requests.

Right now, this will allow us to add request IDs to the
requestIntercepted DevTools event (Bug 899386) and add request IDs to
the new cookie information DevTools events (Bug 856777)

In order to move the rest of our network events to the browser
(Bug 849483), I am planning on extending this new optional request ID to
include other DevTools request metadata, such as the initiator chain.

Bug: 899386, 849483, 856777
Change-Id: Ib92fcbd6da3b418a635cdef164dc1fad98d8ce26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1535292
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Matt Menke <mmenke@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Reviewed-by: Pavel Feldman <pfeldman@chromium.org>
Commit-Queue: Joey Arhar <jarhar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#648335}
10 files changed