Roll src/third_party/shaderc/src 6d9f753c1d15..8a7efb5da88a (2 commits)

https://chromium.googlesource.com/external/github.com/google/shaderc/+log/6d9f753c1d15..8a7efb5da88a

git log 6d9f753c1d15..8a7efb5da88a --date=short --first-parent --format='%ad %ae %s'
2020-02-05 rharrison@google.com Add in support for spvc logging to the terminal (#981)
2020-02-05 rharrison@google.com Rolling 4 dependencies and updated expectations (#983)

Created with:
  gclient setdep -r src/third_party/shaderc/src@8a7efb5da88a

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/shaderc-chromium-autoroll
Please CC 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/+/master/autoroll/README.md

Bug: None
Tbr: radial-bots+chrome-roll@google.com
Change-Id: I74498266e926975c8f2eb490ca0d2087e651d1af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2040922Reviewed-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@{#738856}

DEPS

@@ -298,7 +298,7 @@ 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.
-  'shaderc_revision': '6d9f753c1d15adbf711571410b2b14dc20ec6ac1',
+  'shaderc_revision': '8a7efb5da88a67cd2f2a3096abe12c0b146abb6e',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.