Mesa 19.0.0 will be soon released, and we should get that for disco, and then follow point-releases until the last one is released (roughly next July, will need an SRU).
We'll also migrate it to use LLVM 8.
New features according to upstream release notes:
GL_AMD_texture_texture4 on all GL 4.0 drivers.
GL_EXT_shader_implicit_conversions on all drivers (ES extension).
GL_EXT_texture_compression_bptc on all GL 4.0 drivers (ES extension).
GL_EXT_texture_compression_rgtc on all GL 3.0 drivers (ES extension).
GL_EXT_render_snorm on gallium drivers (ES extension).
GL_EXT_texture_view on drivers supporting texture views (ES extension).
GL_OES_texture_view on drivers supporting texture views (ES extension).
GL_NV_shader_atomic_float on nvc0 (Fermi/Kepler only).
Shader-based software implementations of GL_ARB_gpu_shader_fp64, GL_ARB_gpu_shader_int64, GL_ARB_vertex_attrib_64bit, and GL_ARB_shader_ballot on i965.
VK_ANDROID_external_memory_android_hardware_buffer on Intel
Fixed and re-exposed VK_EXT_pci_bus_info on Intel and RADV
VK_EXT_scalar_block_layout on Intel and RADV
VK_KHR_depth_stencil_resolve on Intel
VK_KHR_draw_indirect_count on Intel
VK_EXT_conditional_rendering on Intel
VK_EXT_memory_budget on RADV
this is available on ppa:canonical-
though it's built with proposed enabled, so could need bits from there