When a frame is empty, still write the captured context for that
frame because the index file will contain the frame file, and the
replay will execute the according swapbuffer so that the replay will
query the context serialization when testing trace correctness.

With that enable RobustResourceInitTest.SurfaceInitializedAfterSwap/*
for capture/replay.

Bug: angleproject:5939
Change-Id: Ib280d55f739cc2bb8d2da0919e98c37a2cd576ba
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2987991
Commit-Queue: Gert Wollny <gert.wollny@collabora.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>