Update stable to r5251.

git-svn-id: http://webrtc.googlecode.com/svn/stable/talk@5252 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/app/webrtc/java/jni/peerconnection_jni.cc b/app/webrtc/java/jni/peerconnection_jni.cc
index 0b7c78b..75f230f 100644
--- a/app/webrtc/java/jni/peerconnection_jni.cc
+++ b/app/webrtc/java/jni/peerconnection_jni.cc
@@ -61,6 +61,7 @@
 #include <map>
 #include <sys/prctl.h>
 #include <sys/syscall.h>
+#include <unistd.h>
 
 #include "talk/app/webrtc/mediaconstraintsinterface.h"
 #include "talk/app/webrtc/peerconnectioninterface.h"