Roll src/third_party/webrtc 4f3c4fcb1f26..a08b2384a324 (3 commits)

https://webrtc.googlesource.com/src.git/+log/4f3c4fcb1f26..a08b2384a324

git log 4f3c4fcb1f26..a08b2384a324 --date=short --first-parent --format='%ad %ae %s'
2020-02-28 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 45a3ae97..73a39687 (745356:745464)
2020-02-28 guidou@webrtc.org Add RTC_EXPORT to VCMEncodedFrame
2020-02-28 titovartem@webrtc.org Extract BWE stats collection.

Created with:
  gclient setdep -r src/third_party/webrtc@a08b2384a324

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: I7570f4bc1c7f3426443cc934a651d1a4a5dbbac0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2080721Reviewed-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@{#745655}

DEPS

@@ -1431,7 +1431,7 @@ deps = {
     Var('chromium_git') + '/external/github.com/gpuweb/cts.git' + '@' + 'ec18cc3262922e7dcdbe70243c6f40606f979144',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '4f3c4fcb1f26606af9e7ce0420d1fa8fbc95d82f',
+    Var('webrtc_git') + '/src.git' + '@' + 'a08b2384a3245082cd40e8682676252ebebb1fe8',
 
   'src/third_party/libgifcodec':
      Var('skia_git') + '/libgifcodec' + '@'+  Var('libgifcodec_revision'),