Causing failures on the Intel and AMD bots which seem to have incorrect rounding for 1-bit alpha formats.

This reverts commit 0bcb68f3.

Change-Id: I00d333b5c10ba3f41d54bec95769f4baf07b0771
Reviewed-on: https://chromium-review.googlesource.com/288206Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Geoff Lang <geofflang@chromium.org>