Only happens with texture formats that require initialization.

BUG=angleproject:1069
TEST=dEQP-GLES3.functional.texture.format.sized.2d_array.* all pass

Change-Id: I215d1262cddcde4ed218b6f023e67747cbc3eeaf
Reviewed-on: https://chromium-review.googlesource.com/285347Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Brandon Jones <bajones@google.com>