DevTools: [Audits] Send messages from child targets to proxy connections.

Related: https://github.com/GoogleChrome/lighthouse/pull/9783

Bug: 1011228
Change-Id: I8c232c8f440df72d3780dc66a03166cddc9f5287
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1838310
Commit-Queue: Connor Clark <cjamcl@google.com>
Reviewed-by: Benedikt Meurer <bmeurer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#704425}
3 files changed