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These objects are not used when the passthrough command decoder is in
use.  This saves several GPU memory allocations in TextureManager for
default and black textures.

Saves ~2 MB per context.

This is a reland of https://chromium-review.googlesource.com/c/chromium/src/+/2028291

TBR=sandersd@chromium.org

BUG=1046613
BUG=1030835

Change-Id: Iae138dd860023d3b16e958fed290ad78188b31bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2072358
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Auto-Submit: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745174}