Revert "Roll src/third_party/webrtc/ 83d27683a..31cee3a0d (7 commits)"

This reverts commit 1d862dda.

Reason for revert: broke WinMSVC64 (dbg) compile:

histogram_percentile_counter.obj : error LNK2019: unresolved external symbol "struct rtc::nullopt_t const rtc::nullopt" (?nullopt@rtc@@3Unullopt_t@1@B) referenced in function "public: class rtc::Optional<unsigned int> __cdecl rtc::HistogramPercentileCounter::GetPercentile(float)" (?GetPercentile@HistogramPercentileCounter@rtc@@QEAA?AV?$Optional@I@2@M@Z)
rate_statistics.obj : error LNK2001: unresolved external symbol "struct rtc::nullopt_t const rtc::nullopt" (?nullopt@rtc@@3Unullopt_t@1@B)
string_to_number.obj : error LNK2001: unresolved external symbol "struct rtc::nullopt_t const rtc::nullopt" (?nullopt@rtc@@3Unullopt_t@1@B)


Original change's description:
> Roll src/third_party/webrtc/ 83d27683a..31cee3a0d (7 commits)
> 
> https://webrtc.googlesource.com/src.git/+log/83d27683a83d..31cee3a0d51e
> 
> $ git log 83d27683a..31cee3a0d --date=short --no-merges --format='%ad %ae %s'
> 
> Created with:
>   roll-dep src/third_party/webrtc
> BUG=None,None
> 
> 
> 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: Idbcb75f5fe9f49ddb5b3f8718dbfe8b2dfb698a3
> Reviewed-on: https://chromium-review.googlesource.com/806321
> Reviewed-by: WebRTC Roll Bot <webrtc-autoroll@chromium.org>
> Commit-Queue: WebRTC Roll Bot <webrtc-autoroll@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#521486}

TBR=webrtc-autoroll@chromium.org,webrtc-chromium-sheriffs-robots@google.com

Change-Id: Ibe6c064ed64c8563c6e86b07ac655c3dcee159ac
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: None
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/807208Reviewed-by: Derek Cheng <imcheng@chromium.org>
Commit-Queue: Derek Cheng <imcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521504}

DEPS

@@ -634,7 +634,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '05591bbeae6592fd924caec8e728a4ea86cbb8c9',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '31cee3a0d51eed2417dabb7d88ec19ef59444d86', # commit position 20628
+    Var('webrtc_git') + '/src.git' + '@' + '83d27683a83d8c4307ca9275779e822cb4604ccf', # commit position 20628
 
   'src/third_party/xdg-utils': {
       'url': Var('chromium_git') + '/chromium/deps/xdg-utils.git' + '@' + 'd80274d5869b17b8c9067a1022e4416ee7ed5e0d',