Note that storage buffer and readonly storage buffer may not be
supported in vertex shader on OpenGL backend. In OpenGL Spec 4.6,
the minimum value of MAX_VERTEX_SHADER_STORAGE_BLOCKS is 0.
BUG=dawn:180, dawn:284
Change-Id: Ib637a61e4eee0a0996c0da33f492e075fd94e1e7
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/14380
Commit-Queue: Yunchao He <yunchao.he@intel.com>
Reviewed-by: Austin Eng <enga@chromium.org>