GitLab

Allows the WebEngine to connect to an Agent-published MetricsRecorder
service.

Some simplification of CastRunner code, eliminating the need for an
alternate constructor for "isolated runners" by decoupling service
publishing from runner construction.

Added an integration test.

Bug: 1060768
Change-Id: Ia36a13cbd9a68565bd80bb32facf393b23d3cfb7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2133056
Commit-Queue: Kevin Marshall <kmarshall@chromium.org>
Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#758107}