Don't call Texture::onDestroy twice for the zero textures.
Don't call Texture::onDestroy twice for the zero textures.

The BindingPointer will call onDestroy when all references are removed, no
need to do it explicitly.

BUG=angleproject:3070

Change-Id: Ic5dd4da8f73e204d26d9d3a3c6e1eff9fded5411
Reviewed-on: https://chromium-review.googlesource.com/c/1409868
Reviewed-by: Jamie Madill <7e492b4f1c8458024932de3ba475cbf015424c30@chromium.org>
Commit-Queue: Geoff Lang <b6fc25fe0362055230985c05cbfa8adb741ccc0f@chromium.org>

ppy/angle,ppy/angle,ppy/angle,ppy/angle