Trace replay: Call glFinish before screenshots On some platforms we're getting partial or no results in the screenshot, even though it ends up displaying correctly on screen. Adding a glFinish before glReadPixels clears up the issue. Bug: b/42263221 Change-Id: Id5d2384c01fece1f7cd4d79b7cc599d082fb2864 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5824180 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Roman Lavrov <romanl@google.com> Auto-Submit: Cody Northrop <cnorthrop@google.com>