If a clear is deffered on the swapchain image, then the clear should be
applied before swap takes effect.

Bug: angleproject:5262
Change-Id: I61aa8ab2983258a02c25a150e6d8c2d2bdbdf97a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2506780Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Mohan Maiya <m.maiya@samsung.com>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>