Roll spirv-headers and spirv-tools

Roll src/third_party/spirv-headers/src/ 2c512180c..dcf23bdab (1 commit)

$ git log 2c512180c..dcf23bdab --date=short --no-merges --format='%ad %ae %s'
2018-09-06 cepheus Headers for revision 4 of SPIR-V 1.3, including SPV_KHR_vulkan_memory_model.

Roll src/third_party/SPIRV-Tools/src/ 21bcb9d8b..7600fc0e1 (2 commits)

$ git log 21bcb9d8b..7600fc0e1 --date=short --no-merges --format='%ad %ae %s'
2018-09-05 dneto Update Dim capabilities
2018-06-01 dneto Support SPV_KHR_vulkan_memory_model rev2

Created with:
  roll-dep src/third_party/SPIRV-Tools/src

TBR=dneto@chromium.org

Change-Id: Idd3e61f9aaa01a5787465fefc20f2c232d828a08
Reviewed-on: https://chromium-review.googlesource.com/1211428
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589312}
1 file changed