Will be used for logging GL/EGL debug messages.

Bug: angleproject:3505
Change-Id: I10ff32dd4f9227cabac2f3d9425b0428e7af1398
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1648714Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>