Roll src/third_party/webrtc 6c371ca7005a..21f6fd79ad05 (2 commits)

https://webrtc.googlesource.com/src.git/+log/6c371ca7005a..21f6fd79ad05


git log 6c371ca7005a..21f6fd79ad05 --date=short --no-merges --format='%ad %ae %s'
2019-04-04 jakobi@webrtc.org Add preemptive rate and preferred buffer size plots to event log visualizer.
2019-04-04 gustaf@webrtc.org AEC3: Remove unused config parameters


Created with:
  gclient setdep -r src/third_party/webrtc@21f6fd79ad05

The AutoRoll server is located here: https://autoroll.skia.org/r/webrtc-chromium-autoroll

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.



BUG=chromium:None
TBR=webrtc-chromium-sheriffs-robots@google.com

Change-Id: Ib6de7e58af4c8c72ff7cff37b71eb38bfa44d889
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1553029Reviewed-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@{#647759}

DEPS

@@ -1343,7 +1343,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '688fbfe33779392aa210d67d4aa12cb012f112c2',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '6c371ca7005adde9812d9527bea64f552cf53867',
+    Var('webrtc_git') + '/src.git' + '@' + '21f6fd79ad058fc7f33f989eec67a60c77157fea',
 
   'src/third_party/xdg-utils': {
       'url': Var('chromium_git') + '/chromium/deps/xdg-utils.git' + '@' + 'd80274d5869b17b8c9067a1022e4416ee7ed5e0d',