Roll src/third_party/SPIRV-Tools/src 9b3cc3e05337..19b256616d96 (3 commits)

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git/+log/9b3cc3e05337..19b256616d96

git log 9b3cc3e05337..19b256616d96 --date=short --no-merges --format='%ad %ae %s'
2019-09-04 zoddicus@users.noreply.github.com For WebGPU<->Vulkan optimization, set correct execution environment (#2834)
2019-09-04 40687079+rumblehhh@users.noreply.github.com Export SPIRV-Tools targets on installation (#2785)
2019-09-04 jmadill@chromium.org GN: Add Chromium GoogleTest deps. (#2832)

Created with:
  gclient setdep -r src/third_party/SPIRV-Tools/src@19b256616d96

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/spirv-tools-chromium-autoroll
Please CC radial-bots+chrome-roll@google.com,jmadill@chromium.org,jmadill@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

CQ_INCLUDE_TRYBOTS=luci.chromium.try:android_angle_vk32_deqp_rel_ng;luci.chromium.try:android_angle_vk32_rel_ng;luci.chromium.try:android_angle_vk64_deqp_rel_ng;luci.chromium.try:android_angle_vk64_rel_ng;luci.chromium.try:linux_angle_deqp_rel_ng;luci.chromium.try:linux-angle-rel;luci.chromium.try:win-angle-rel-32;luci.chromium.try:win-angle-rel-64;luci.chromium.try:win-angle-deqp-rel-32;luci.chromium.try:win-angle-deqp-rel-64
TBR=radial-bots+chrome-roll@google.com,jmadill@chromium.org,jmadill@google.com

Bug: None
Change-Id: I4f45ef71c638ee96c6515e264f1643aa2f76e08c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1787441Reviewed-by: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Commit-Queue: chromium-autoroll <chromium-autoroll@skia-public.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#693637}

DEPS

@@ -281,7 +281,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.
-  'spv_tools_revision': '9b3cc3e05337358d0bd9fec1b7a51e3cbf55312b',
+  'spv_tools_revision': '19b256616d96bdad580c036bc8619706bc177d96',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.