Roll SPIRV-Tools from 8a0ebd40f86d to c278dada96d9 (5 revisions)

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Tools.git/+log/8a0ebd40f86d..c278dada96d9

2020-09-02 stefanomil@google.com spirv-fuzz: Fix GetIdEquivalenceClasses (#3767)
2020-09-02 stefanomil@google.com spirv-fuzz: Replace id in OpPhi coming from a dead predecessor (#3744)
2020-09-01 stefanomil@google.com spirv-fuzz: Transformation to replace the use of an irrelevant id (#3697)
2020-09-01 vasniktel@gmail.com spirv-fuzz: TransformationMutatePointer (#3737)
2020-09-01 stefanomil@google.com spirv-fuzz: Compute interprocedural loop nesting depth of blocks (#3753)

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 cwallez@google.com,radial-bots+chrome-roll@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/+doc/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: cwallez@google.com,radial-bots+chrome-roll@google.com
Change-Id: I07b4464acb921342ad66d0730956a61253e90ed5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2389780Reviewed-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@{#803818}

DEPS

@@ -302,7 +302,7 @@ 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': '8a0ebd40f86d1f18ad42ea96c6ac53915076c3c7',
+  'spv_tools_revision': 'c278dada96d98310ce0bf2dc50b14c85f197568b',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.