Roll src/third_party/webrtc 4f2783b9fe77..16cec3be2c96 (3 commits)

https://webrtc.googlesource.com/src.git/+log/4f2783b9fe77..16cec3be2c96

git log 4f2783b9fe77..16cec3be2c96 --date=short --no-merges --format='%ad %ae %s'
2019-10-25 philipel@webrtc.org Added allow_codec_switching parameter to RTCConfig.
2019-10-25 hbos@webrtc.org Revert "[PeerConnection] Use an OperationsChain in PeerConnection for async ops."
2019-10-25 danilchap@webrtc.org Cleanup PacketBuffer tests to use immediate result

Created with:
  gclient setdep -r src/third_party/webrtc@16cec3be2c96

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

TBR=webrtc-chromium-sheriffs-robots@google.com

Bug: chromium:None
Change-Id: I6ba84d5eefe5239bd1e88d5e9889de1ee3ccd0b2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1881168Reviewed-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@{#709458}

DEPS

@@ -1509,7 +1509,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '2701c130839edbeb226735b0775966b6423d9e83',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '4f2783b9fe778ec8852432eade83c31bc8a31239',
+    Var('webrtc_git') + '/src.git' + '@' + '16cec3be2c96d7db74e5cb6a9d9837e98d09944e',
 
   # Wuffs' canonical repository is at github.com/google/wuffs, but we use
   # Skia's mirror of Wuffs, the same as in upstream Skia's DEPS file.