Revert "Roll AppRTC 3168981..e7f6cae"

This reverts commit bb14af8a299248d1471d4cfc5b63922297665fea in
https://codereview.chromium.org/1509873002/

Reason: collider fails to build:
________ running '/usr/bin/python webrtc.DEPS/build_apprtc_collider.py' in '/mnt/data/b/build/slave/Linux_Builder/build'
src/out/go-workspace/src/collider/collider.go:55: undefined: tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384
src/out/go-workspace/src/collider/collider.go:59: undefined: tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384
Traceback (most recent call last):
  File "webrtc.DEPS/build_apprtc_collider.py", line 43, in <module>
    sys.exit(main())
  File "webrtc.DEPS/build_apprtc_collider.py", line 38, in main
    env=golang_env)
  File "/usr/lib/python2.7/subprocess.py", line 511, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command '['go/bin/go', 'get', 'collidermain']' returned non-zero exit status 2
Error: Command '/usr/bin/python webrtc.DEPS/build_apprtc_collider.py' returned non-zero exit status 1 in /mnt/data/b/build/slave/Linux_Builder/build

BUG=567598
TBR=phoglund@chromium.org

Review URL: https://codereview.chromium.org/1508853004 .
diff --git a/DEPS b/DEPS
index ca2e3cd..c53c21e 100644
--- a/DEPS
+++ b/DEPS
@@ -8,7 +8,7 @@
 
 deps = {
   'apprtc':
-    Var('git_url') + '/external/webrtc/apprtc@e7f6cae744590cc2191e50fe673a0cca5d55b226',
+    Var('git_url') + '/external/webrtc/apprtc@3168981efed7629fabee731a5ee74d3716b50652',
   'webrtc.DEPS/third_party/manifestdestiny':
     Var('git_url') + '/chromium/deps/manifestdestiny.git@46ae53ac463e23bfefec374a81806355ea598ac4',
   'webrtc.DEPS/third_party/mozdownload':