Roll src/third_party/webrtc 6adb0a26846c..d7bf5c56b69b (4 commits)

https://webrtc.googlesource.com/src.git/+log/6adb0a26846c..d7bf5c56b69b

git log 6adb0a26846c..d7bf5c56b69b --date=short --no-merges --format='%ad %ae %s'
2019-10-23 mbonadei@webrtc.org Revert "Define WEBRTC_ENABLE_SYMBOL_EXPORT if is_component_build=true."
2019-10-23 mbonadei@webrtc.org Reland "Define WEBRTC_ENABLE_SYMBOL_EXPORT if is_component_build=true."
2019-10-23 danilchap@webrtc.org change PacketBuffer to return it's result rather that use callback
2019-10-23 chromium-webrtc-autoroll@webrtc-ci.iam.gserviceaccount.com Roll chromium_revision 6dc3a51e..b5030084 (708537:708640)

Created with:
  gclient setdep -r src/third_party/webrtc@d7bf5c56b69b

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,chromium:None
Change-Id: I7bd0d1650c7147745e0b051076aba23c45aa9a05
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876968Reviewed-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@{#708785}

DEPS

@@ -1509,7 +1509,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '2701c130839edbeb226735b0775966b6423d9e83',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '6adb0a26846c0a6ddf7d7e72ebf80b829c34d693',
+    Var('webrtc_git') + '/src.git' + '@' + 'd7bf5c56b69b7a34f13802f100940e38ee47bad4',
 
   # Wuffs' canonical repository is at github.com/google/wuffs, but we use
   # Skia's mirror of Wuffs, the same as in upstream Skia's DEPS file.