Create a private API for controlling WebRTC's AEC3

chrome/common/extensions/api/webrtc_audio_private.idl

Index: chrome/common/extensions/api/webrtc_audio_private.idl
diff --git a/chrome/common/extensions/api/webrtc_audio_private.idl b/chrome/common/extensions/api/webrtc_audio_private.idl
index 32afbd48ee9288b4e4fac6c9807775132584a8e7..8235ef6fd38e1f8359b173adb9a91d3b3e55524a 100644
--- a/chrome/common/extensions/api/webrtc_audio_private.idl
+++ b/chrome/common/extensions/api/webrtc_audio_private.idl
@@ -50,6 +50,11 @@ namespace webrtcAudioPrivate {
     long? guestProcessId;
   };
 
+  dictionary AudioExperiments {
+    // Enables or disables the new acoustic echo canceller (AEC3) in WebRTC.
+    boolean? enableAec3;
+  };
+
   interface Functions {
     // Retrieves a list of available audio sink devices.
     static void getSinks(GetSinksCallback callback);
@@ -75,6 +80,14 @@ namespace webrtcAudioPrivate {
     static void getAssociatedSink(DOMString securityOrigin,
                                   DOMString sourceIdInOrigin,
                                   SinkIdCallback cb);
+
+    // For a given requesting process |request| and a security origin
+    // |securityOrigin|, provides settings to experiments related to WebRTC
+    // audio. The experiment settings are passed in the |audioExperiments|
+    // dictionary.

[Devlin, 2017/04/11 20:49:37]

For IDL files, comments should be formatted like so:
// <high level description>
// |<param-1>|: <param-1 description>
...
// |<param-n>|: <param-n description>

so for this, e.g.:

// Sets the active experiments.
// |request|: Information about the requesting process.
// |securityOrigin|: The origin to restrict the settings to.
// |audioExperiments|: The experiments to enable or disable.

[hlundin-chromium, 2017/04/12 05:54:16]

Done.

+    static void setAudioExperiments(RequestInfo request,
+                                    DOMString securityOrigin,
+                                    AudioExperiments audioExperiments);
   };
 
   interface Events {