Roll src/third_party/webrtc 1b20c41dcbfb..d19513f3ffbb (3 commits)

https://webrtc.googlesource.com/src.git/+log/1b20c41dcbfb..d19513f3ffbb

git log 1b20c41dcbfb..d19513f3ffbb --date=short --first-parent --format='%ad %ae %s'
2020-03-25 titovartem@google.com Move calculation of target_encode_bitrate to DefaultVideoQualityAnalyzer
2020-03-25 sprang@webrtc.org Fixes temporal rate allocation issues.
2020-03-25 thakis@chromium.org webrtc: Suppress a -Wunreachable-code warning on Android.

Created with:
  gclient setdep -r src/third_party/webrtc@d19513f3ffbb

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:346399
Tbr: webrtc-chromium-sheriffs-robots@google.com
Change-Id: I42d17e4608f938a52a142005732ea17cd3a78f5b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2120523Reviewed-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@{#753227}

DEPS

@@ -1448,7 +1448,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/gpuweb/cts.git' + '@' + '84ee597cdeae08bb26e578fc66a35bcf35f633f4',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '1b20c41dcbfb4f9320cffe43f22a887dc30bd53b',
+    Var('webrtc_git') + '/src.git' + '@' + 'd19513f3ffbb939fd56b5377b678bb31d3154e14',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),