Roll WebRTC from 78e9acd96726 to 804db2dde3f1 (4 revisions)

https://webrtc.googlesource.com/src.git/+log/78e9acd96726..804db2dde3f1

2020-09-16 kwiberg@webrtc.org UntypedFunction: Eliminate an unnecessary indirection in the implementation
2020-09-16 hta@webrtc.org Test for negotiating pre-stopped M-sections.
2020-09-16 peah@webrtc.org Allow the SwapQueue to utilize user-define swap capability
2020-09-16 hta@webrtc.org Don't expect a transceiver for stopped m-sections

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:1127625
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: Ib273380e67f4ec6b635087f301fd64ea343d4371
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2415010Reviewed-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@{#807619}

DEPS

@@ -1471,7 +1471,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '78e9acd9672649f2660ebd054bd1ce16828d992f',
+    Var('webrtc_git') + '/src.git' + '@' + '804db2dde3f13834891d11b47dc0f0e18b9d6320',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),