Fix AllocationSequence to handle the case when TurnPort stops using shared socket.

webrtc/p2p/base/turnport_unittest.cc

Index: webrtc/p2p/base/turnport_unittest.cc
diff --git a/webrtc/p2p/base/turnport_unittest.cc b/webrtc/p2p/base/turnport_unittest.cc
index 2c93ead9dfacb701c042ab7cc85d594fa991de72..901d25cdb238b24a0e4b77685df247ca4877e7d8 100644
--- a/webrtc/p2p/base/turnport_unittest.cc
+++ b/webrtc/p2p/base/turnport_unittest.cc
@@ -665,6 +665,13 @@ TEST_F(TurnPortTest, TestTurnAllocateMismatch) {
 
   // Verifies that the new port has a different address now.
   EXPECT_NE(first_addr, turn_port_->socket()->GetLocalAddress());
+
+  // Verify that all packets received from the shared socket are ignored.
+  std::string test_packet = "Test packet";
+  EXPECT_FALSE(turn_port_->HandleIncomingPacket(
+      socket_.get(), test_packet.data(), test_packet.size(),
+      rtc::SocketAddress(kTurnUdpExtAddr.ipaddr(), 0),
+      rtc::CreatePacketTime(0)));
 }
 
 // Tests that a shared-socket-TurnPort creates its own socket after