Capture/Replay: Fix extra frame captured with trigger. A prior CL erroneously removed the -1 from the trigger frame count. Restore this to ensure we capture the right number of frames. Bug: angleproject:5133 Change-Id: Ic24404fbfeb8578badd6204db8316f081eafaa53 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3104693 Reviewed-by: Cody Northrop <cnorthrop@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>