Vulkan: Create a pre-rotation test for 400x300 windows This test reproduces the cause of the failures with the following dEQP tests: dEQP.GLES31/functional_texture_multisample_samples_*_sample_position This CL also fixes a problem with the previous test, and puts the common rendering/ReadPixels code in a common method. Bug: b/156395519 Change-Id: Id38476b6caf6f25c52f7504187fb500a39109438 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2207550 Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Ian Elliott <ianelliott@google.com>