Restore spv::CapabilityShaderViewportIndexLayerEXT

shaderc has been updated.

MA-437 # done

Change-Id: Ib90c1d3e6d8a02f0ea94e086dfcc0df71da34c19
diff --git a/layers/shader_validation.cpp b/layers/shader_validation.cpp
index 94479a3..4188556 100644
--- a/layers/shader_validation.cpp
+++ b/layers/shader_validation.cpp
@@ -1206,8 +1206,7 @@
         {spv::CapabilityDrawParameters, {VK_KHR_SHADER_DRAW_PARAMETERS_EXTENSION_NAME, nullptr, &E::vk_khr_shader_draw_parameters}},
         {spv::CapabilityGeometryShaderPassthroughNV, {VK_NV_GEOMETRY_SHADER_PASSTHROUGH_EXTENSION_NAME, nullptr, &E::vk_nv_geometry_shader_passthrough}},
         {spv::CapabilitySampleMaskOverrideCoverageNV, {VK_NV_SAMPLE_MASK_OVERRIDE_COVERAGE_EXTENSION_NAME, nullptr, &E::vk_nv_sample_mask_override_coverage}},
-        //TODO(MA-437) restore this when glslang is updated
-        //{spv::CapabilityShaderViewportIndexLayerEXT, {VK_EXT_SHADER_VIEWPORT_INDEX_LAYER_EXTENSION_NAME, nullptr, &E::vk_ext_shader_viewport_index_layer}},
+        {spv::CapabilityShaderViewportIndexLayerEXT, {VK_EXT_SHADER_VIEWPORT_INDEX_LAYER_EXTENSION_NAME, nullptr, &E::vk_ext_shader_viewport_index_layer}},
         {spv::CapabilityShaderViewportIndexLayerNV, {VK_NV_VIEWPORT_ARRAY2_EXTENSION_NAME, nullptr, &E::vk_nv_viewport_array2}},
         {spv::CapabilityShaderViewportMaskNV, {VK_NV_VIEWPORT_ARRAY2_EXTENSION_NAME, nullptr, &E::vk_nv_viewport_array2}},
         {spv::CapabilitySubgroupBallotKHR, {VK_EXT_SHADER_SUBGROUP_BALLOT_EXTENSION_NAME, nullptr, &E::vk_ext_shader_subgroup_ballot }},