Enable the Java wrapper to load different .so library.

webrtc/sdk/android/api/org/webrtc/PeerConnectionFactoryDatachannelOnly.java

+/*
+ *  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.
+ */
+
+package org.webrtc;
+
+import java.util.List;
+
+/**
+ * The subclass of PeerConnectionFactoryBase loading with the datachannel only shared library
+ * support. Main entry point to the PeerConnection API for clients.
+ */
+public class PeerConnectionFactoryDatachannelOnly extends PeerConnectionFactoryBase {

[Taylor Brandstetter, 2017/05/11 10:17:11]

Could the class still be called "PeerConnectionFactory", so that an application
could switch to the "datachannel_only" build targets without having to change
any code?

+  static {
+    try {
+      System.loadLibrary("jingle_peerconnection_datachannel_only_so");

[Taylor Brandstetter, 2017/05/11 10:17:11]

Is the only difference this line of code? If so, why not just have a
"PeerConnectionLibary" class with a single method, "getLibraryName", which
PeerConnectionFactory calls? Then the build targets would either compile a
"PeerConnectionLibrary.java" or "PeerConnectionLibaryDataChannelOnly.java", and
each of those files would be really small. Or is there a reason this wouldn't
work?

+      nativeLibLoaded = true;
+    } catch (UnsatisfiedLinkError t) {
+      nativeLibLoaded = false;
+    }
+  }
+
+  // Must be called at least once before creating a PeerConnectionFactory
+  // (for example, at application startup time).
+  public static void initializeAndroidGlobals(
+      android.content.Context context, boolean videoHwAcceleration) {
+    PeerConnectionFactoryBase.initializeAndroidGlobals(context, videoHwAcceleration);
+  }
+  // Field trial initialization. Must be called before PeerConnectionFactory
+  // is created.
+  public static void initializeFieldTrials(String fieldTrialsInitString) {
+    PeerConnectionFactoryBase.initializeFieldTrials(fieldTrialsInitString);
+  }
+  // Wrapper of webrtc::field_trial::FindFullName. Develop the feature with default behaviour off.
+  // Example usage:
+  // if (PeerConnectionFactory.fieldTrialsFindFullName("WebRTCExperiment").equals("Enabled")) {
+  //   method1();
+  // } else {
+  //   method2();
+  // }
+  public static String fieldTrialsFindFullName(String name) {
+    return PeerConnectionFactoryBase.fieldTrialsFindFullName(name);
+  }
+  // Internal tracing initialization. Must be called before PeerConnectionFactory is created to
+  // prevent racing with tracing code.
+  public static void initializeInternalTracer() {
+    PeerConnectionFactoryBase.initializeInternalTracer();
+  }
+  // Internal tracing shutdown, called to prevent resource leaks. Must be called after
+  // PeerConnectionFactory is gone to prevent races with code performing tracing.
+  public static void shutdownInternalTracer() {
+    PeerConnectionFactoryBase.shutdownInternalTracer();
+  }
+  // Start/stop internal capturing of internal tracing.
+  public static boolean startInternalTracingCapture(String tracing_filename) {
+    return PeerConnectionFactoryBase.startInternalTracingCapture(tracing_filename);
+  }
+  public static void stopInternalTracingCapture() {
+    PeerConnectionFactoryBase.stopInternalTracingCapture();
+  }
+
+  @Deprecated
+  public PeerConnectionFactoryDatachannelOnly() {
+    super();
+  }
+
+  public PeerConnectionFactoryDatachannelOnly(Options options) {
+    super(options);
+  }
+}