Roll src/third_party/shaderc/src 621605ce2644..05b285760e40 (2 commits)

https://chromium.googlesource.com/external/github.com/google/shaderc/+log/621605ce2644..05b285760e40

git log 621605ce2644..05b285760e40 --date=short --no-merges --format='%ad %ae %s'
2019-10-09 rharrison@google.com Rolling 5 dependencies (#836)
2019-10-09 rharrison@google.com Add spvc compiler to returned result (#828)

Created with:
  gclient setdep -r src/third_party/shaderc/src@05b285760e40

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

TBR=radial-bots+chrome-roll@google.com

Bug: None
Change-Id: I7d82ab364210d15bcbac2beaa1b6702f172516e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1850104Reviewed-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@{#704336}

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': '621605ce2644d55ab74cb27a8afef97dc40f1b0f',
+  'shaderc_revision': '05b285760e40a324001fb1fb66b396c1fffb7bc5',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.