Relanding: Break peerconnection_jni.cc into multiple files, in "pc" directory.

webrtc/sdk/android/src/jni/pc/datachannelobserver_jni.h

+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_SDK_ANDROID_SRC_JNI_PC_DATACHANNELOBSERVER_JNI_H_
+#define WEBRTC_SDK_ANDROID_SRC_JNI_PC_DATACHANNELOBSERVER_JNI_H_
+
+#include "webrtc/api/datachannelinterface.h"
+#include "webrtc/sdk/android/src/jni/jni_helpers.h"
+
+namespace webrtc_jni {
+
+// Adapter for a Java DataChannel$Observer presenting a C++ DataChannelObserver
+// and dispatching the callback from C++ back to Java.
+class DataChannelObserverJni : public webrtc::DataChannelObserver {
+ public:
+  DataChannelObserverJni(JNIEnv* jni, jobject j_observer);
+  virtual ~DataChannelObserverJni() {}
+
+  void OnBufferedAmountChange(uint64_t previous_amount) override;
+  void OnStateChange() override;
+  void OnMessage(const webrtc::DataBuffer& buffer) override;
+
+ private:
+  const ScopedGlobalRef<jobject> j_observer_global_;
+  const ScopedGlobalRef<jclass> j_observer_class_;
+  const ScopedGlobalRef<jclass> j_buffer_class_;
+  const jmethodID j_on_buffered_amount_change_mid_;
+  const jmethodID j_on_state_change_mid_;
+  const jmethodID j_on_message_mid_;
+  const jmethodID j_buffer_ctor_;
+};
+
+}  // namespace webrtc_jni
+
+#endif  // WEBRTC_SDK_ANDROID_SRC_JNI_PC_DATACHANNELOBSERVER_JNI_H_