Roll src/third_party/webrtc 51bf20029462..5740f3e2b8fd (2 commits)

https://webrtc.googlesource.com/src.git/+log/51bf20029462..5740f3e2b8fd

git log 51bf20029462..5740f3e2b8fd --date=short --no-merges --format='%ad %ae %s'
2019-10-11 danilchap@webrtc.org Clarify expectation on GlobalLock
2019-10-11 gustaf@webrtc.org Fix bypass of unnecessary resampling

Created with:
  gclient setdep -r src/third_party/webrtc@5740f3e2b8fd

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:b/130016532
Change-Id: Ide7481d7dc71f8be9efe552a36d4d825b052f8e6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1855471Reviewed-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@{#705123}

DEPS

@@ -1470,7 +1470,7 @@ deps = {
     Var('chromium_git') + '/external/khronosgroup/webgl.git' + '@' + '2701c130839edbeb226735b0775966b6423d9e83',
 
   'src/third_party/webrtc':
-    Var('webrtc_git') + '/src.git' + '@' + '51bf200294622a45444b68ad1498a41f8a860df3',
+    Var('webrtc_git') + '/src.git' + '@' + '5740f3e2b8fdee7288748907920d9fabe948e895',
 
   'src/third_party/xdg-utils': {
       'url': Var('chromium_git') + '/chromium/deps/xdg-utils.git' + '@' + 'd80274d5869b17b8c9067a1022e4416ee7ed5e0d',