Add a test for imageLoad after glClear to the texture Bug: angleproject:7355 Change-Id: Ib1ddf685f2fa6cb24161615224971a7185234000 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3659504 Auto-Submit: Chris Dalton <chris@rive.app> Reviewed-by: Kenneth Russell <kbr@chromium.org> Commit-Queue: Kenneth Russell <kbr@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>