Add test for copying GL_SRGB8_ALPHA8 to GL_RGBA8 The pixel values should be the same (no conversion should happen). Include sub-tests with and without alpha premultiplication. Bug: angleproject:7907 Change-Id: I2e3d657d5b8513cd06df357e84027572ebce03ff Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/4852258 Commit-Queue: ccameron chromium <ccameron@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>