When using a sampler the texture was created as if it has mipmaps,
regardless what you specified in GL_TEXTURE_MIN_FILTER via
glSamplerParameteri() -- mistakenly the default value
GL_NEAREST_MIPMAP_LINEAR or the value set via glTexParameteri() was
evaluated.
If you didn't provide mipmaps and didn't let the driver generate them
this led to not sampling your texture data when minification occurred.

BUG=angleproject:2772
TEST=angle_end2end_tests.Texture2DTestES3.MinificationWithSamplerNoMipmapping

Change-Id: I195147e208129c6fa8686bb0d9aea6931b2f20b1
Reviewed-on: https://chromium-review.googlesource.com/1175910
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>