Add a simple, safe gain PostProcessor.

chromecast/media/cma/backend/alsa/post_processors/governor_create.cc

Index: chromecast/media/cma/backend/alsa/post_processors/governor_create.cc
diff --git a/chromecast/media/cma/backend/alsa/post_processors/governor_create.cc b/chromecast/media/cma/backend/alsa/post_processors/governor_create.cc
new file mode 100644
index 0000000000000000000000000000000000000000..358a0eeaaba641feb198364d9272090044ba749c
--- /dev/null
+++ b/chromecast/media/cma/backend/alsa/post_processors/governor_create.cc
@@ -0,0 +1,13 @@
+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromecast/media/cma/backend/alsa/post_processors/governor.h"
+#include "chromecast/public/media/audio_post_processor_shlib.h"
+
+chromecast::media::AudioPostProcessor* AudioPostProcessorShlib_Create(
+    const std::string& config,
+    int channels) {
+  return static_cast<chromecast::media::AudioPostProcessor*>(
+      new chromecast::media::Governor(config, channels));
+}