Roll WebRTC from 3a5742c880b4 to 3cc1a6509bf6 (2 revisions)

https://webrtc.googlesource.com/src.git/+log/3a5742c880b4..3cc1a6509bf6

2020-05-20 jianj@google.com Set av1 speed from resolution.
2020-05-20 mbonadei@webrtc.org Add ios_code_signing_identity_description to GN args.

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: I060ab7bc0c14275a5198927082a4a2c207de46f1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2210909Reviewed-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@{#770898}

DEPS

@@ -1453,7 +1453,7 @@ deps = {
   },
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '3a5742c880b42003be39652a7ea060c29c322a7f',
+    Var('webrtc_git') + '/src.git' + '@' + '3cc1a6509bf6143f9d52d76a7648a9c8d3bdccea',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),