Create a private API for controlling WebRTC's AEC3

content/public/test/mock_render_process_host.cc

Index: content/public/test/mock_render_process_host.cc
diff --git a/content/public/test/mock_render_process_host.cc b/content/public/test/mock_render_process_host.cc
index 232282d5086962ac833b1e1a2b3b3cfaad7e5414..cb56a8373d8b14b111108b1121d69a84845040b7 100644
--- a/content/public/test/mock_render_process_host.cc
+++ b/content/public/test/mock_render_process_host.cc
@@ -353,6 +353,8 @@ bool MockRenderProcessHost::StopWebRTCEventLog() {
   return false;
 }
 
+void MockRenderProcessHost::SetEchoCanceller3(bool enable) {}
+
 void MockRenderProcessHost::SetWebRtcLogMessageCallback(
     base::Callback<void(const std::string&)> callback) {
 }