Roll src/third_party/webrtc 46b3bc6c24c2..2b7d96959916 (8 commits)

https://webrtc.googlesource.com/src.git/+log/46b3bc6c24c2..2b7d96959916

git log 46b3bc6c24c2..2b7d96959916 --date=short --first-parent --format='%ad %ae %s'
2020-05-14 handellm@webrtc.org RtpVideoSender: remove lock recursions.
2020-05-14 handellm@webrtc.org RtpSenderEgress: remove lock recursions.
2020-05-14 handellm@webrtc.org AudioProcessingImpl: remove lock recursions.
2020-05-14 titovartem@webrtc.org Revert "Make sure that "current" rtc::Thread instances are always current for TaskQueueBase."
2020-05-14 titovartem@webrtc.org Revert "Revert back to using the task_queue_ for guarding access."
2020-05-14 danilo.bargen@threema.ch objc: Export RTCStatistics and RTCStatisticsReport
2020-05-14 tommi@webrtc.org Revert back to using the task_queue_ for guarding access.
2020-05-14 rgl@google.com Reland "Add an optional override for AudioRecord device"

Created with:
  gclient setdep -r src/third_party/webrtc@2b7d96959916

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

Bug: None
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: I4b9d23a21861b0794f3d966ab598cbb936f44872
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2202004Reviewed-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@{#768908}

DEPS

@@ -1453,7 +1453,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '46b3bc6c24c233fe41a2401ce6e8eb8204a2d5a8',
+    Var('webrtc_git') + '/src.git' + '@' + '2b7d96959916306cb267899a219cbd20ec24b841',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),