Extracting NetLog inner classes into their own classes.

net/socket/tcp_client_socket.h

Index: net/socket/tcp_client_socket.h
diff --git a/net/socket/tcp_client_socket.h b/net/socket/tcp_client_socket.h
index 159c458e49a44705274dbf2efeafcf9b9b1f0f22..295e8b68113950afda1d7f0379b840a4bfdf4c1b 100644
--- a/net/socket/tcp_client_socket.h
+++ b/net/socket/tcp_client_socket.h
@@ -14,13 +14,14 @@
 #include "net/base/address_list.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_export.h"
-#include "net/log/net_log.h"
 #include "net/socket/connection_attempts.h"
 #include "net/socket/stream_socket.h"
 #include "net/socket/tcp_socket.h"
 
 namespace net {
 
+class NetLog;
+struct NetLogSource;
 class SocketPerformanceWatcher;
 
 // A client socket that uses TCP as the transport layer.
@@ -33,7 +34,7 @@ class NET_EXPORT TCPClientSocket : public StreamSocket {
       const AddressList& addresses,
       std::unique_ptr<SocketPerformanceWatcher> socket_performance_watcher,
       net::NetLog* net_log,
-      const net::NetLog::Source& source);
+      const net::NetLogSource& source);
 
   // Adopts the given, connected socket and then acts as if Connect() had been
   // called. This function is used by TCPServerSocket and for testing.