Create a private API for controlling WebRTC's AEC3

content/browser/renderer_host/render_process_host_impl.h

Index: content/browser/renderer_host/render_process_host_impl.h
diff --git a/content/browser/renderer_host/render_process_host_impl.h b/content/browser/renderer_host/render_process_host_impl.h
index 4405d667996f47a12fcb91145c8edf5d2647c2b9..20ffac1b32cc3383d03fad56f7507606e7306930 100644
--- a/content/browser/renderer_host/render_process_host_impl.h
+++ b/content/browser/renderer_host/render_process_host_impl.h
@@ -156,6 +156,7 @@ class CONTENT_EXPORT RenderProcessHostImpl
   void DisableAudioDebugRecordings() override;
   bool StartWebRTCEventLog(const base::FilePath& file_path) override;
   bool StopWebRTCEventLog() override;
+  void SetEchoCanceller3(bool enable) override;
   void SetWebRtcLogMessageCallback(
       base::Callback<void(const std::string&)> callback) override;
   void ClearWebRtcLogMessageCallback() override;
@@ -565,6 +566,12 @@ class CONTENT_EXPORT RenderProcessHostImpl
   WebRtcStopRtpDumpCallback stop_rtp_dump_callback_;
 
   WebRTCEventLogHost webrtc_eventlog_host_;
+
+  // When this variable is not set, the use of AEC3 is governed by the Finch
+  // experiment and/or WebRTC's own default. When set to true/false, Finch and
+  // WebRTC defaults will be overridden, and AEC3/AEC2 (respectively) will be
+  // used.
+  base::Optional<bool> override_aec3_;

[Henrik Grunell, 2017/04/10 18:08:13]

Actually, I realized that this belongs in AecDumpMessageFilter on the render
side. The reason the AEC dump is handled in this class at consumer registration
is that a file needs to be opened here on the browser side. That's not the case
for the AEC3 override obviously, so it can be closer to where it's used.

So, please move it there. (see other comment.)

[hlundin-chromium, 2017/04/11 09:19:37]

Done.

 #endif
 
   // Forwards messages between WebRTCInternals in the browser process