Add GLSL support for runtime-sized arrays in SSBOs The GLSL parser now allows a runtime-sized array as the last member in a shader storage block. Clamping indexing against the memory bounds is done by determining the array length at runtime. Runtime-sized arrays are used in dEQP tests for many compute shader tests, so these now work on the OpenGL backend. BUG=angleproject:1951 TEST=angle_unittests, dEQP-GLES31.functional.shaders.linkage.shader_storage_block.* dEQP-GLES31.functional.shaders.builtin_functions.*compute* Change-Id: Ibecca24623ca8e4723af6f0e0421fe9711ea828d Reviewed-on: https://chromium-review.googlesource.com/787976 Commit-Queue: Olli Etuaho <oetuaho@nvidia.com> Reviewed-by: Corentin Wallez <cwallez@chromium.org>