Added validation to disallow usage of geometry shaders without a vertex shader Bug: angleproject:5579 Test: KHR-GLES32.core.geometry_shader.api.fs_gs_draw_call Test: KHR-GLES32.core.geometry_shader.api.pipeline_program_without_active_vs Change-Id: Ieeec544d514ac772416ab0427c1c1c5058276f98 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2796151Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
