Use field_trial::IsEnabled for FlexFEC.

webrtc/media/engine/internalencoderfactory.cc

Index: webrtc/media/engine/internalencoderfactory.cc
diff --git a/webrtc/media/engine/internalencoderfactory.cc b/webrtc/media/engine/internalencoderfactory.cc
index 544070fc4c3c7e8b35ea1b7c3086513c4fee1d74..a8d4f2d2c2c935282d0699cb0aeaabb441b54653 100644
--- a/webrtc/media/engine/internalencoderfactory.cc
+++ b/webrtc/media/engine/internalencoderfactory.cc
@@ -23,11 +23,12 @@ namespace {
 
 // If this field trial is enabled, the "flexfec-03" codec will be advertised
 // as being supported by the InternalEncoderFactory. This means that
-// "flexfec-03" will appear in the default local SDP, and we therefore need to
-// be ready to receive FlexFEC packets from the remote.
+// "flexfec-03" will appear in the default SDP offer, and we therefore need to
+// be ready to receive FlexFEC packets from the remote. It also means that
+// FlexFEC SSRCs will be generated by MediaSession and added as "a=ssrc:" and
+// "a=ssrc-group:" lines in the local SDP.
 bool IsFlexfecAdvertisedFieldTrialEnabled() {
-  return webrtc::field_trial::FindFullName("WebRTC-FlexFEC-03-Advertised") ==
-         "Enabled";
+  return webrtc::field_trial::IsEnabled("WebRTC-FlexFEC-03-Advertised");
 }
 
 }  // namespace