Adding second layer of the echo canceller 3 functionality.

webrtc/modules/audio_processing/aec3/echo_path_variability.h

Index: webrtc/modules/audio_processing/aec3/echo_path_variability.h
diff --git a/webrtc/modules/audio_processing/aec3/echo_path_variability.h b/webrtc/modules/audio_processing/aec3/echo_path_variability.h
new file mode 100644
index 0000000000000000000000000000000000000000..a1d21dce8ab5ef53437a591dfb1012bd76cd06a5
--- /dev/null
+++ b/webrtc/modules/audio_processing/aec3/echo_path_variability.h
@@ -0,0 +1,25 @@
+/*
+ *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.

[hlundin-webrtc, 2017/01/18 13:08:49]

2017

[peah-webrtc, 2017/01/19 15:33:05]

Done.

+ *
+ *  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_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_VARIABILITY_H_
+#define WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_VARIABILITY_H_
+
+namespace webrtc {
+
+struct EchoPathVariability {
+  EchoPathVariability(bool gain_change, bool delay_change);
+  bool AudioPathChanged() const;
+  bool gain_change;
+  bool delay_change;
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_AUDIO_PROCESSING_AEC3_ECHO_PATH_VARIABILITY_H_