In OpenGL ES, it is possible to sample from level 0 of a mipmapped
texture by setting GL_TEXTURE_MIN_FILTER to GL_NEAREST.

This is possible in D3D9 and D3D11 Feature Level 10_0+ via various
methods. It's not possible in D3D11 Feature Level 9_3, though.
This change works around this restriction by creating two copies of
each texture on 9_3. The textures are identical, except one has
mipmaps and one doesn't.

The D3D11 renderer figures out which texture to use at the right
time, and keeps the textures in sync with each other as necessary.
Note: each texture is only created when it's needed. It's possible
that only one (or even neither) D3D texture will be created for a
given GL texture.

Change-Id: I3c17137b4f63b9158b3abf067ad8e5d5c49d2191
Reviewed-on: https://chromium-review.googlesource.com/234522Tested-by: Austin Kinross <aukinros@microsoft.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>