diff --git a/media/base/codec.h b/media/base/codec.h
index 036a1722a6..228acad07a 100644
--- a/media/base/codec.h
+++ b/media/base/codec.h
@@ -28,7 +28,7 @@
 
 namespace cricket {
 
-typedef std::map<std::string, std::string> CodecParameterMap;
+using CodecParameterMap = std::map<std::string, std::string>;
 
 class FeedbackParam {
  public:
@@ -187,6 +187,9 @@ struct RTC_EXPORT Codec {
 using VideoCodec = Codec;
 using AudioCodec = Codec;
 
+using VideoCodecs = std::vector<Codec>;
+using AudioCodecs = std::vector<Codec>;
+
 Codec CreateAudioCodec(int id,
                        const std::string& name,
                        int clockrate,
diff --git a/pc/session_description.h b/pc/session_description.h
index 044fccf9c0..403e46529f 100644
--- a/pc/session_description.h
+++ b/pc/session_description.h
@@ -43,10 +43,8 @@
 
 namespace cricket {
 
-typedef std::vector<AudioCodec> AudioCodecs;
-typedef std::vector<VideoCodec> VideoCodecs;
-typedef std::vector<CryptoParams> CryptoParamsVec;
-typedef std::vector<webrtc::RtpExtension> RtpHeaderExtensions;
+using CryptoParamsVec = std::vector<CryptoParams>;
+using RtpHeaderExtensions = std::vector<webrtc::RtpExtension>;
 
 // Options to control how session descriptions are generated.
 const int kAutoBandwidth = -1;
@@ -258,8 +256,9 @@ class MediaContentDescription {
   }
 
  protected:
-  // TODO(bugs.webrtc.org/15214): move all RTP related things to a subclass that
-  // the SCTP content description does not inherit from.
+  // TODO(bugs.webrtc.org/15214): move all RTP related things to
+  // RtpMediaDescription that the SCTP content description does
+  // not inherit from.
   std::string protocol_;
 
  private:
@@ -290,9 +289,7 @@ class MediaContentDescription {
   std::vector<Codec> codecs_;
 };
 
-template <class C>
-class MediaContentDescriptionImpl : public MediaContentDescription {};
-using RtpMediaContentDescription = MediaContentDescriptionImpl<Codec>;
+class RtpMediaContentDescription : public MediaContentDescription {};
 
 class AudioContentDescription : public RtpMediaContentDescription {
  public: