Roll src/third_party/webrtc 5dca3f1336a6..c31a4ec66af2 (2 commits)

https://webrtc.googlesource.com/src.git/+log/5dca3f1336a6..c31a4ec66af2

git log 5dca3f1336a6..c31a4ec66af2 --date=short --first-parent --format='%ad %ae %s'
2020-01-30 ivoc@webrtc.org Disable opus tests to allow upgrade to opus 1.3
2020-01-30 srte@webrtc.org Default disables legacy overhead calculation.

Created with:
  gclient setdep -r src/third_party/webrtc@c31a4ec66af2

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/webrtc-chromium-autoroll
Please CC webrtc-chromium-sheriffs-robots@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: webrtc-chromium-sheriffs-robots@google.com
Change-Id: Id95f4d958bb6315e0b42686f69d6a425a93e1f34
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031132Reviewed-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@{#736920}

DEPS

@@ -1494,7 +1494,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/gpuweb/cts.git' + '@' + 'ec18cc3262922e7dcdbe70243c6f40606f979144',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '5dca3f1336a6d18633aea31b043ca4466bbae33b',
+    Var('webrtc_git') + '/src.git' + '@' + 'c31a4ec66af2b0ee28112d5b4df006771e23157f',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),