H264 codec: Check profile-level-id when matching

webrtc/media/base/mediaconstants.cc

Index: webrtc/media/base/mediaconstants.cc
diff --git a/webrtc/media/base/mediaconstants.cc b/webrtc/media/base/mediaconstants.cc
index 0f31864ede12081b777477d582398463245c711f..640c67e8938556f106b1092799445e8f702a6a11 100644
--- a/webrtc/media/base/mediaconstants.cc
+++ b/webrtc/media/base/mediaconstants.cc
@@ -97,6 +97,9 @@ const char kH264CodecName[] = "H264";
 
 // RFC 6184 RTP Payload Format for H.264 video
 const char kH264FmtpProfileLevelId[] = "profile-level-id";
+// If no profile-level-id is present as a parameter, the Baseline Profile
+// without additional constraints at Level 1 is implied.
+const char kH264FmtpDefaultProfileLevelId[] = "42000a";
 const char kH264FmtpLevelAsymmetryAllowed[] = "level-asymmetry-allowed";
 const char kH264FmtpPacketizationMode[] = "packetization-mode";
 const char kH264ProfileLevelConstrainedBaseline[] = "42e01f";