Clean up capture interface.

Start/end is a little odd, changed to start/stop.

Change-Id: I91a4b74013133de27c87f6c79e992eb10851def0
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/583956
Commit-Queue: Jim Van Verth <jvanverth@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
9 files changed