Roll src/third_party/webrtc c6b2f34f358b..55c991cc81ae (4 commits)

https://webrtc.googlesource.com/src.git/+log/c6b2f34f358b..55c991cc81ae

git log c6b2f34f358b..55c991cc81ae --date=short --first-parent --format='%ad %ae %s'
2020-04-02 marinaciocea@webrtc.org [InsertableStreams] Save the transformer to be set on Reconfigure.
2020-04-02 ilnik@webrtc.org Calculate video padding for vp9 in the same way as for vp8
2020-04-02 sakal@webrtc.org Delete legacy MediaCodec HW codec integration.
2020-04-02 titovartem@google.com Extract test peer creation into separate file

Created with:
  gclient setdep -r src/third_party/webrtc@55c991cc81ae

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: chromium:1052765
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: I657effd393041139590d6737c7aebae11fb48c0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134353Reviewed-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@{#755884}

DEPS

@@ -1458,7 +1458,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'c6b2f34f358b70f5fdd4b119b77b88f0f33492a8',
+    Var('webrtc_git') + '/src.git' + '@' + '55c991cc81ae26e43e94f56c218f9254436aa269',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),