Improve D3D11 FL9_3 zero-LOD workaround (e.g. TextureCubes)

D3D11 Feature Level 9_3 can't disable mipmaps on a mipmapped
texture, and sample from level zero of it. A previous commit
added a workaround for this in ANGLE to Texture2Ds. This
commit fixes some minor issues in that commit, and extends
the workaround to apply to TextureCubes too.

Change-Id: Ic97321af6f8bbf7ad5d96e58655c342db3978a6a
Reviewed-on: https://chromium-review.googlesource.com/241944
Tested-by: Austin Kinross <aukinros@microsoft.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
diff --git a/tests/angle_tests/CubeMapTextureTest.cpp b/tests/angle_tests/CubeMapTextureTest.cpp
index d1db7e7..b1561d9 100644
--- a/tests/angle_tests/CubeMapTextureTest.cpp
+++ b/tests/angle_tests/CubeMapTextureTest.cpp
@@ -1,7 +1,7 @@
 #include "ANGLETest.h"
 
 // Use this to select which configurations (e.g. which renderer, which GLES major version) these tests should be run against.
-ANGLE_TYPED_TEST_CASE(CubeMapTextureTest, ES2_D3D11);
+ANGLE_TYPED_TEST_CASE(CubeMapTextureTest, ES2_D3D11, ES2_D3D11_FL9_3);
 
 template<typename T>
 class CubeMapTextureTest : public ANGLETest