Revert "Roll src/third_party/webrtc/ 823f9135f..a5b903833 (1 commit)"

This reverts commit 1b89887a.

Reason for revert: Apparently causes compilation failure on iOS bots.
See https://ci.chromium.org/buildbot/chromium.mac/ios-device-xcode-clang/59633

Original change's description:
> Roll src/third_party/webrtc/ 823f9135f..a5b903833 (1 commit)
> 
> https://webrtc.googlesource.com/src.git/+log/823f9135f858..a5b903833f88
> 
> $ git log 823f9135f..a5b903833 --date=short --no-merges --format='%ad %ae %s'
> 
> Created with:
>   roll-dep src/third_party/webrtc
> 
> 
> The AutoRoll server is located here: https://webrtc-chromium-roll.skia.org
> 
> Documentation for the AutoRoller is here:
> https://skia.googlesource.com/buildbot/+/master/autoroll/README.md
> 
> If the roll is causing failures, please contact the current sheriff, who should
> be CC'd on the roll, and stop the roller if necessary.
> 
> 
> CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_archive_rel_ng;master.tryserver.chromium.mac:mac_chromium_archive_rel_ng
> TBR=webrtc-chromium-sheriffs-robots@google.com
> 
> Change-Id: I93fc64657ce737b93f6ded1f7bf95a1ab27dc518
> Reviewed-on: https://chromium-review.googlesource.com/1046927
> Reviewed-by: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
> Commit-Queue: webrtc-chromium-autoroll <webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
> Cr-Commit-Position: refs/heads/master@{#556431}

TBR=webrtc-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com,webrtc-chromium-sheriffs-robots@google.com

Change-Id: I60a4ac7b083df5c4c617e3324773b43d43de59b5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_archive_rel_ng;master.tryserver.chromium.mac:mac_chromium_archive_rel_ng
Reviewed-on: https://chromium-review.googlesource.com/1047166Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Commit-Queue: Guido Urdaneta <guidou@chromium.org>
Cr-Commit-Position: refs/heads/master@{#556442}

DEPS

@@ -968,7 +968,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '7c0541da63f571512c49758cbc0767117997a270',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'a5b903833f8810bd4d4dd291e08df9f3f9e1b51e', # commit position 21742
+    Var('webrtc_git') + '/src.git' + '@' + '823f9135f858c9fc7526e29a180818ad7f0d408c', # commit position 21742
 
   'src/third_party/xdg-utils': {
       'url': Var('chromium_git') + '/chromium/deps/xdg-utils.git' + '@' + 'd80274d5869b17b8c9067a1022e4416ee7ed5e0d',