Roll WebRTC from fc6b87192db6 to ec9b281bbc14 (16 revisions)

https://webrtc.googlesource.com/src.git/+log/fc6b87192db6..ec9b281bbc14

2021-01-07 titovartem@google.com Add ability to specify random seed when creating built it network emulation
2021-01-07 danilchap@webrtc.org Introduce CopyOnWriteBuffer::MutableData() function
2021-01-07 alessiob@webrtc.org SSE2 and NEON kill switches for AGC2
2021-01-07 philipp.hancke@googlemail.com video_engine: fix logging
2021-01-07 perkj@webrtc.org Move setting of encoder bitrate allocation callback type to VideoSendStream
2021-01-07 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision e2c7dc77..25be8f6b (840733:840938)
2021-01-07 webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com Update WebRTC code version (2021-01-07T04:03:27).
2021-01-06 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 6504b345..e2c7dc77 (840589:840733)
2021-01-06 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 24b4cef3..6504b345 (840473:840589)
2021-01-06 mbonadei@webrtc.org Add hta@ to rtc_base/ and api/ WATCHLISTS.
2021-01-06 mbonadei@webrtc.org Remove kwiberg@ from WATCHLIST.
2021-01-06 webrtc-version-updater@webrtc-ci.iam.gserviceaccount.com Update WebRTC code version (2021-01-06T04:02:29).
2021-01-06 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 49b7dc5e..24b4cef3 (840329:840473)
2021-01-05 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision c87d4517..49b7dc5e (840164:840329)
2021-01-05 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 4ae11810..c87d4517 (840025:840164)
2021-01-05 terelius@webrtc.org Add static constexpr type to RTC event log events.

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: I4db24386b3e5cbba55794fe608293ff33f19e904
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2615982Reviewed-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@{#841208}

DEPS

@@ -1518,7 +1518,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/gpuweb/cts.git' + '@' + '3c2fe3888658d82b47ca831d59a2e07579619c2d',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'fc6b87192db6d5e4fd6997814f00b6792cf16180',
+    Var('webrtc_git') + '/src.git' + '@' + 'ec9b281bbc14fe9c3cd2b27241059f52b7eb654a',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),