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 85e10a91504d0a24e65601c28b1c24344064310d..1e138f6b945962467e1735b2b50ec26582db07ac 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);