Roll WebRTC from 5d2bf19be865 to 20422daa8281 (2 revisions)

https://webrtc.googlesource.com/src.git/+log/5d2bf19be865..20422daa8281

2020-12-30 mbonadei@webrtc.org mac: Pull arm64 gn binary on M1 hosts.
2020-12-30 danilchap@webrtc.org Fix potential 32bit integer overflow on rtcp receiver report

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/+doc/master/autoroll/README.md

Bug: chromium:1103319
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: Ia7a4b95c1876f208527b2dc3e442ad0ee77d9f0a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2607866Reviewed-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@{#839847}

DEPS

@@ -1514,7 +1514,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/gpuweb/cts.git' + '@' + '3c2fe3888658d82b47ca831d59a2e07579619c2d',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '5d2bf19be865c19ae09b21b32771ccda3c95eda0',
+    Var('webrtc_git') + '/src.git' + '@' + '20422daa8281e5792a9d2c947990788b66ea9551',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),