Support a user-provided string for the TLS ALPN extension.

webrtc/p2p/base/packetsocketfactory.h

Index: webrtc/p2p/base/packetsocketfactory.h
diff --git a/webrtc/p2p/base/packetsocketfactory.h b/webrtc/p2p/base/packetsocketfactory.h
index 60f0ae058055c04ec06c833bcc789252f55c9143..e66a4afc0962f726085d4944610491f06bebbb0f 100644
--- a/webrtc/p2p/base/packetsocketfactory.h
+++ b/webrtc/p2p/base/packetsocketfactory.h
@@ -16,6 +16,12 @@
 
 namespace rtc {
 
+// This structure contains options required to create TCP packet sockets.
+struct PacketSocketTcpOptions {
+  int opts;
+  std::vector<std::string> tls_alpn_protocols;
+};
+
 class AsyncPacketSocket;
 class AsyncResolverInterface;
 
@@ -45,7 +51,7 @@ class PacketSocketFactory {
       uint16_t max_port,
       int opts) = 0;
 
-  // TODO: |proxy_info| and |user_agent| should be set
+  // TODO(deadbeef): |proxy_info| and |user_agent| should be set
   // per-factory and not when socket is created.
   virtual AsyncPacketSocket* CreateClientTcpSocket(
       const SocketAddress& local_address,
@@ -54,6 +60,21 @@ class PacketSocketFactory {
       const std::string& user_agent,
       int opts) = 0;
 
+  // TODO(deadbeef): |proxy_info|, |user_agent| and |tcp_options| should
+  // be set per-factory and not when socket is created.
+  // TODO(deadbeef): Implement this method in all subclasses (namely those in
+  // Chromium), make pure virtual, and remove the old CreateClientTcpSocket.
+  virtual AsyncPacketSocket* CreateClientTcpSocket(
+      const SocketAddress& local_address,
+      const SocketAddress& remote_address,
+      const ProxyInfo& proxy_info,
+      const std::string& user_agent,
+      const PacketSocketTcpOptions& tcp_options) {
+    return CreateClientTcpSocket(local_address, remote_address, proxy_info,
+                                 user_agent, tcp_options.opts);
+  }
+
+
   virtual AsyncResolverInterface* CreateAsyncResolver() = 0;
 
  private: