Roll webrtc 6174:6187.

BUG=371805
TBR=mcasas@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/291923003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271456 0039d316-1c4b-4281-b951-d872f2087c98

DEPS

@@ -55,7 +55,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling WebRTC
   # and V8 without interference from each other.
-  "webrtc_revision": "6174",
+  "webrtc_revision": "6187",
   "jsoncpp_revision": "248",
   "nss_revision": "267366",
   # Three lines of non-changing comments so that