Roll WebRTC from d74c0e600a7f to fc4668dae26e (2 revisions)

https://webrtc.googlesource.com/src.git/+log/d74c0e600a7f..fc4668dae26e

2020-07-17 philipp.hancke@googlemail.com configure target bitrate in opus dtx tests
2020-07-17 sprang@webrtc.org Allows bitrate prober to discard delayed probes, unit type refactorings

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: Ic24f325d280b69349f826fb7c0bff7defde302f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2304375Reviewed-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@{#789481}

DEPS

@@ -1480,7 +1480,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'd74c0e600a7f5bc43c2bcb75d4903b3038677459',
+    Var('webrtc_git') + '/src.git' + '@' + 'fc4668dae26e1c9ad40eb75919e7e733251fda4b',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),