Adding "first packet received" notification to PeerConnectionObserver.

talk/app/webrtc/java/jni/peerconnection_jni.cc

Index: talk/app/webrtc/java/jni/peerconnection_jni.cc
diff --git a/talk/app/webrtc/java/jni/peerconnection_jni.cc b/talk/app/webrtc/java/jni/peerconnection_jni.cc
index 5ea63f74aecbb8e86b46f3abc20bf72dca7205b5..1980f72a0d3c7dbc152e804d217a3bb85bf73535 100644
--- a/talk/app/webrtc/java/jni/peerconnection_jni.cc
+++ b/talk/app/webrtc/java/jni/peerconnection_jni.cc
@@ -374,6 +374,14 @@ class PCOJava : public PeerConnectionObserver {
     CHECK_EXCEPTION(jni()) << "error during CallVoidMethod";
   }
 
+  void OnFirstMediaPacketReceived() override {
+    ScopedLocalRefFrame local_ref_frame(jni());
+    jmethodID m = GetMethodID(jni(), *j_observer_class_,

[AlexG, 2016/01/22 02:40:54]

nit: alignment

+                              "onFirstMediaPacketReceived", "()V");
+    jni()->CallVoidMethod(*j_observer_global_, m);
+    CHECK_EXCEPTION(jni()) << "error during CallVoidMethod";
+  }
+
   void SetConstraints(ConstraintsWrapper* constraints) {
     RTC_CHECK(!constraints_.get()) << "constraints already set!";
     constraints_.reset(constraints);