It's required on Chrome OS.
Based on spec EXT_texture_format_BGRA8888, this format is renderable.

Bug: angleproject:4594
Change-Id: Ibde0f0de18f4b8079a23f4b13123c6b5c8794a89
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2172638Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Jiajia Qin <jiajia.qin@intel.com>