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