Previously, the alpha channel was not set which resulted the intended
swapchain buffer format is B8G8R8X8_UNORM. It means that the format
supports 8 bits for each color channel and 8 bits unused. However, in
our test case, we expect to compare the alpha channel. So we should
set alpha channel explicitly.
Bug: angleproject:4575
Bug: angleproject:4576
Change-Id: Ic26ee81a6a34dc44d0ae32e3dc463e9afa16e05c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2237189
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
