Roll src/third_party/webrtc 3d1647412c08..c1c6284cd11f (3 commits)

https://webrtc.googlesource.com/src.git/+log/3d1647412c08..c1c6284cd11f

git log 3d1647412c08..c1c6284cd11f --date=short --no-merges --format='%ad %ae %s'
2019-09-17 nisse@webrtc.org New (empty) build target api:media_stream_interface
2019-09-16 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 3cf04de..2e4ccff (696812:696956)
2019-09-16 dinosaurav@chromium.org Refactor Rtp Receivers to accept SSRC 0.

Created with:
  gclient setdep -r src/third_party/webrtc@c1c6284cd11f

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

TBR=webrtc-chromium-sheriffs-robots@google.com

Bug: chromium:None
Change-Id: I62e738167c00c9f355ee282fc485982662302d4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808785
Reviewed-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@{#697172}

DEPS

@@ -1425,7 +1425,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + 'abaae129d9a0c6e1e092067e0b105475df43352e',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '3d1647412c08f589b03aed641a3cca5f0b05555d',
+    Var('webrtc_git') + '/src.git' + '@' + 'c1c6284cd11f6021ec775f9b1c44264594af8212',
 
   'src/third_party/xdg-utils': {
       'url': Var('chromium_git') + '/chromium/deps/xdg-utils.git' + '@' + 'd80274d5869b17b8c9067a1022e4416ee7ed5e0d',