GitLab

Deleted a comment in MessageService::OpenChannelImpl that
questioned the use of |guest_process_id| and
|guest_render_frame_routing_id|. These ID appear to be used by some
component extensions (bug 424762) so they cannot be removed.

Review-Url: https://codereview.chromium.org/2529213002
Cr-Commit-Position: refs/heads/master@{#439504}