Schedule a CreatePermissionRequest after the success of a previous request
unless a channel binding request is already scheduled.

BUG=5178
R=pthatcher@webrtc.org

Review URL: https://codereview.webrtc.org/1434603002 .

Cr-Commit-Position: refs/heads/master@{#10625}
diff --git a/webrtc/p2p/base/stunrequest.cc b/webrtc/p2p/base/stunrequest.cc
index df5614d..0a0b1a8 100644
--- a/webrtc/p2p/base/stunrequest.cc
+++ b/webrtc/p2p/base/stunrequest.cc
@@ -53,6 +53,14 @@
   }
 }
 
+void StunRequestManager::Flush() {
+  for (const auto kv : requests_) {
+    StunRequest* request = kv.second;
+    thread_->Clear(request, MSG_STUN_SEND);
+    thread_->Send(request, MSG_STUN_SEND, NULL);
+  }
+}
+
 void StunRequestManager::Remove(StunRequest* request) {
   ASSERT(request->manager() == this);
   RequestMap::iterator iter = requests_.find(request->id());