The new validation added in http://crbug.com/809237 failed to consider
that sampler object state overrides texture object state if a sampler
object is bound. State caching makes this complicated to fix.

Fixes WebGL conformance test incompatible-texture-type-for-sampler.html
https://github.com/KhronosGroup/WebGL/pull/2823

Bug: 940080, 809237
Change-Id: I26b0fb35c5630c36248edae80f0298a0cb7e14b8
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1522364
Commit-Queue: James Darpinian <jdarpinian@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>