Add RtcEventLog to AppRTCMobile with preference setting.

Enable diagnostic packet and event recording as in the "webrtc-internal"
setting in Chromium.

Bug: webrtc:8859
Change-Id: I1d4a19e0dd60133cdd0d4e18a55780623b65653c
Reviewed-on: https://webrtc-review.googlesource.com/49541
Commit-Queue: Qingsi Wang <qingsi@google.com>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21987}

examples/androidapp/src/org/appspot/apprtc/RtcEventLog.java

@@ -0,0 +1,74 @@
+/*
+ *  Copyright 2018 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.
+ */
+
+package org.appspot.apprtc;
+
+import android.content.Context;
+import android.os.ParcelFileDescriptor;
+import android.util.Log;
+import java.io.File;
+import java.io.IOException;
+import org.webrtc.PeerConnection;
+
+public class RtcEventLog {
+  private static final String TAG = "RtcEventLog";
+  private static final int OUTPUT_FILE_MAX_BYTES = 10_000_000;
+  private final PeerConnection peerConnection;
+  private RtcEventLogState state = RtcEventLogState.INACTIVE;
+
+  enum RtcEventLogState {
+    INACTIVE,
+    STARTED,
+    STOPPED,
+  }
+
+  public RtcEventLog(PeerConnection peerConnection) {
+    if (peerConnection == null) {
+      throw new NullPointerException("The peer connection is null.");
+    }
+    this.peerConnection = peerConnection;
+  }
+
+  public void start(final File outputFile) {
+    if (state == RtcEventLogState.STARTED) {
+      Log.e(TAG, "RtcEventLog has already started.");
+      return;
+    }
+    final ParcelFileDescriptor fileDescriptor;
+    try {
+      fileDescriptor = ParcelFileDescriptor.open(outputFile,
+          ParcelFileDescriptor.MODE_READ_WRITE | ParcelFileDescriptor.MODE_CREATE
+              | ParcelFileDescriptor.MODE_TRUNCATE);
+    } catch (IOException e) {
+      Log.e(TAG, "Failed to create a new file", e);
+      return;
+    }
+
+    // Passes ownership of the file to WebRTC.
+    boolean success =
+        peerConnection.startRtcEventLog(fileDescriptor.detachFd(), OUTPUT_FILE_MAX_BYTES);
+    if (!success) {
+      Log.e(TAG, "Failed to start RTC event log.");
+      return;
+    }
+    state = RtcEventLogState.STARTED;
+    Log.d(TAG, "RtcEventLog started.");
+  }
+
+  public void stop() {
+    if (state != RtcEventLogState.STARTED) {
+      Log.e(TAG, "RtcEventLog was not started.");
+      return;
+    }
+    peerConnection.stopRtcEventLog();
+    state = RtcEventLogState.STOPPED;
+    Log.d(TAG, "RtcEventLog stopped.");
+  }
+}