Adding second layer of the echo canceller 3 functionality.

webrtc/modules/audio_processing/aec3/echo_path_variability.cc

Index: webrtc/modules/audio_processing/aec3/echo_path_variability.cc
diff --git a/webrtc/modules/audio_processing/aec3/echo_path_variability.cc b/webrtc/modules/audio_processing/aec3/echo_path_variability.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6f5aeb1bb952bb2a6e5723316f3037a335920193
--- /dev/null
+++ b/webrtc/modules/audio_processing/aec3/echo_path_variability.cc
@@ -0,0 +1,22 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/modules/audio_processing/aec3/echo_path_variability.h"
+
+namespace webrtc {
+
+EchoPathVariability::EchoPathVariability(bool gain_change, bool delay_change)

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

Will this struct be expanded later? Otherwise, can you get these definitions
inlined into the h file?

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

Good point. The struct is as it is intended and it worked. 

Done.

+    : gain_change(gain_change), delay_change(delay_change) {}
+
+bool EchoPathVariability::AudioPathChanged() const {
+  return gain_change || delay_change;
+}
+
+}  // namespace webrtc