
Adds a way to enable/disable system trace consumer connections from content, such that we can check whether content's TracingDelegate allows this. Also fixes a few issues with the system tracing DevTools tests, primarily ensuring that the socket overrides are created before the browser initializes. With the new way to enable/disable system consumer connections, the tests are can be extended to cover most Posix platforms (when using a fake system service). Bug: 1141387 Change-Id: I82684e416aabdff9aba6daff4a5784171a615f05 Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2773310 Reviewed-by: Sami Kyöstilä <skyostil@chromium.org> Reviewed-by: Andrey Kosyakov <caseq@chromium.org> Reviewed-by: Avi Drissman <avi@chromium.org> Commit-Queue: Eric Seckler <eseckler@chromium.org> Cr-Commit-Position: refs/heads/master@{#868068}