Roll WebRTC from 11bfeb307c4e to 820021d24600 (2 revisions)

https://webrtc.googlesource.com/src.git/+log/11bfeb307c4e..820021d24600

2020-07-16 danilchap@webrtc.org Ignore fragmentation header when packetizing H264
2020-07-16 handellm@webrtc.org Remove unused critical section includes.

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: None
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: I877271f709b77c2aae5c9defff83b46784a2eef1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2302681Reviewed-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@{#789199}

DEPS

@@ -1475,7 +1475,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '11bfeb307c4e24ecef491ccb35d293df877a95cd',
+    Var('webrtc_git') + '/src.git' + '@' + '820021d24600b8628b8644c43fddf67fa37ccf84',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),