Remove candidates when doing continual gathering

webrtc/p2p/base/port.cc

Index: webrtc/p2p/base/port.cc
diff --git a/webrtc/p2p/base/port.cc b/webrtc/p2p/base/port.cc
index 7993cc02bc082819340ca1e80b974dd91716f995..c6101a53f87a1e5be2dd9809048d193acb729c64 100644
--- a/webrtc/p2p/base/port.cc
+++ b/webrtc/p2p/base/port.cc
@@ -20,6 +20,7 @@
 #include "webrtc/base/helpers.h"
 #include "webrtc/base/logging.h"
 #include "webrtc/base/messagedigest.h"
+#include "webrtc/base/network.h"
 #include "webrtc/base/scoped_ptr.h"
 #include "webrtc/base/stringencode.h"
 #include "webrtc/base/stringutils.h"
@@ -195,6 +196,7 @@ void Port::Construct() {
     ice_username_fragment_ = rtc::CreateRandomString(ICE_UFRAG_LENGTH);
     password_ = rtc::CreateRandomString(ICE_PWD_LENGTH);
   }
+  network_->SignalInactive.connect(this, &Port::OnNetworkInactive);
   LOG_J(LS_INFO, this) << "Port created";
 }
 
@@ -628,6 +630,11 @@ void Port::OnMessage(rtc::Message *pmsg) {
   }
 }
 
+void Port::OnNetworkInactive(const rtc::Network* network) {
+  ASSERT(network == network_);
+  SignalNetworkInactive(this);
+}
+
 std::string Port::ToString() const {
   std::stringstream ss;
   ss << "Port[" << content_name_ << ":" << component_