Add missing ExternalAudioProcessingFactory

stream-webrtc-android/src/main/java/org/webrtc/ExternalAudioProcessingFactory.java

@@ -0,0 +1,31 @@
+package org.webrtc;
+
+public class ExternalAudioProcessingFactory implements AudioProcessingFactory {
+
+  private final String libname;
+
+  public ExternalAudioProcessingFactory(String libname) {
+    if (libname == null) {
+      throw new NullPointerException("libname must not be null.");
+    }
+    if (libname.isEmpty()) {
+      throw new IllegalArgumentException("libname must not be empty.");
+    }
+    this.libname = libname;
+  }
+
+  @Override
+  public long createNative() {
+    return nativeCreateAudioProcessingModule(libname);
+  }
+
+  public void destroyNative() {
+    nativeDestroyAudioProcessingModule();
+  }
+
+  private static native long nativeCreateAudioProcessingModule(String libname);
+
+
+  private static native void nativeDestroyAudioProcessingModule();
+
+}