TracePerfTest: Add ability to screenshot after reset. This patch makes --screenshot-frame take frame arguments that are greater than the frame range of the test. This makes it possible to capture screenshots after reset. E.g. the trace has 100 frames, the argument 1 and 101 should give the same result, but will differ if reset fails. Bug: angleproject:7307 Change-Id: Ie149e6046d0384d93341c677a7b391b5342917d7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3644577 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>