Roll src/third_party/webrtc c347585927b2..1518fd34d888 (2 commits)

https://webrtc.googlesource.com/src.git/+log/c347585927b2..1518fd34d888

git log c347585927b2..1518fd34d888 --date=short --first-parent --format='%ad %ae %s'
2019-12-06 ivoc@webrtc.org Add support for setting a custom NetEqFactory in PeerConnection level tests.
2019-12-06 hofbauer@webrtc.org Expose methods to validate and merge FieldTrial strings.

Created with:
  gclient setdep -r src/third_party/webrtc@1518fd34d888

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: None
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: Id6719bb8c026063d5c0a8d78c5af74b0c1d9ec0f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1955648Reviewed-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@{#722484}

DEPS

@@ -1498,7 +1498,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + 'dd55f3ca8f2ea716ca917a4aaf36f0729fe902b1',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + 'c347585927b2268432f684ed944134db75098299',
+    Var('webrtc_git') + '/src.git' + '@' + '1518fd34d8889bb9c3fbe8d8f9fdfd513a037e68',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),