Add CubeMapBug2 test to trigger Angle bug in validation Add one extra texture sampler in fragment shader and adjust texture binding unit for textures Bug: angleproject:401546698 Change-Id: Ib5c3482a243075a98f1ce1b1f4d4cc9884f5f980 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6458622 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>