Revert of Break peerconnection_jni.cc into multiple files, in "pc" directory.

webrtc/sdk/android/src/jni/pc/rtpreceiverobserver_jni.cc

-/*
- *  Copyright 2017 The WebRTC project authors. All Rights Reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#include "webrtc/sdk/android/src/jni/pc/rtpreceiverobserver_jni.h"
-
-#include "webrtc/sdk/android/src/jni/pc/java_native_conversion.h"
-
-namespace webrtc_jni {
-
-void RtpReceiverObserverJni::OnFirstPacketReceived(
-    cricket::MediaType media_type) {
-  JNIEnv* const jni = AttachCurrentThreadIfNeeded();
-
-  jmethodID j_on_first_packet_received_mid = GetMethodID(
-      jni, GetObjectClass(jni, *j_observer_global_), "onFirstPacketReceived",
-      "(Lorg/webrtc/MediaStreamTrack$MediaType;)V");
-  // Get the Java version of media type.
-  jobject JavaMediaType = NativeToJavaMediaType(jni, media_type);
-  // Trigger the callback function.
-  jni->CallVoidMethod(*j_observer_global_, j_on_first_packet_received_mid,
-                      JavaMediaType);
-  CHECK_EXCEPTION(jni) << "error during CallVoidMethod";
-}
-
-}  // namespace webrtc_jni