Add dependency on libevent where required.

chrome/browser/debugger/devtools_remote_listen_socket.cc

Index: chrome/browser/debugger/devtools_remote_listen_socket.cc
diff --git a/chrome/browser/debugger/devtools_remote_listen_socket.cc b/chrome/browser/debugger/devtools_remote_listen_socket.cc
index 9a2443b6206e38a2238e48b7f9cadadd4d9ea109..e4a84cb546512256ea302bfe1b2c6a8e4fd7bfab 100644
--- a/chrome/browser/debugger/devtools_remote_listen_socket.cc
+++ b/chrome/browser/debugger/devtools_remote_listen_socket.cc
@@ -18,11 +18,6 @@
 #include "base/message_loop.h"
 #include "base/message_pump_libevent.h"
 #include "net/base/net_errors.h"
-#if defined(USE_SYSTEM_LIBEVENT)
-#include <event.h>
-#else
-#include "third_party/libevent/event.h"
-#endif
 #endif
 
 #include "base/eintr_wrapper.h"
@@ -40,7 +35,6 @@
 #define SOCKET int
 const int INVALID_SOCKET = -1;
 const int SOCKET_ERROR = -1;
-struct event;  // From libevent
 #endif
 
 const int kReadBufSize = 200;