Rolling 2 dependencies

Roll src/third_party/shaderc/src/ 4e3bbd9c5..802636496 (1 commit)

https://chromium.googlesource.com/external/github.com/google/shaderc.git/+log/4e3bbd9c5f1a..8026364968ac

$ git log 4e3bbd9c5..802636496 --date=short --no-merges --format='%ad %ae %s'
2020-04-07 rharrison Add concept of comparison sampler to API (#1036)

Roll src/third_party/spirv-cross/spirv-cross/ e58e8d5db..a1d9b474b (6 commits)

https://chromium.googlesource.com/external/github.com/KhronosGroup/SPIRV-Cross.git/+log/e58e8d5dbe03..a1d9b474b5ca

$ git log e58e8d5db..a1d9b474b --date=short --no-merges --format='%ad %ae %s'
2020-04-07 post MSL: Do not use base expression with PhysicalTypeID OpCompositeExtract.
2020-04-03 post Expose a query if samplers or images are comparison resources.
2020-04-03 post Do not add NonWritable/NonReadable decorations for regular images.
2020-04-03 post MSL: Deal with cases where builtin is implicitly needed, declared, but unused.
2020-04-03 post HLSL: Add support for treating NonWritable UAV texture as SRV instead.
2020-04-03 troughton MSL: mark BuiltInFragCoord as implicitly used for subpass reads

Created with:
  roll-dep src/third_party/shaderc/src src/third_party/spirv-cross/spirv-cross

BUG=dawn:367

Change-Id: I02882bc2910b5b8f396af72605813ee20ddaff8d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2141206
Auto-Submit: Ryan Harrison <rharrison@chromium.org>
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757513}

DEPS

@@ -294,11 +294,11 @@ 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.
-  'spirv_cross_revision': 'e58e8d5dbe03ea2cc755dbaf43ffefa1b8d77bef',
+  'spirv_cross_revision': 'a1d9b474b5caae6856c28bf9cde5aaf68e9c11b9',
   # 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': '4e3bbd9c5f1a164add8faca83d28f24c960c752c',
+  'shaderc_revision': '8026364968acb2e55390f6ccf295740ab818ebda',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling feed
   # and whatever else without interference from each other.