RtpPacket class introduced.

webrtc/modules/rtp_rtcp/source/rtp_header_extension.h

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
index 342e38a1f2a969bc25e9d7c38e6a1d67773d511d..beaf989c895830eb3dacc6ecd6bd22ff70d48445 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extension.h
@@ -70,6 +70,8 @@ struct HeaderExtension {
 
 class RtpHeaderExtensionMap {
  public:
+  static constexpr RTPExtensionType kInvalidType = kRtpExtensionNone;
+  static constexpr uint8_t kInvalidId = 0;
   RtpHeaderExtensionMap();
   ~RtpHeaderExtensionMap();
 
@@ -89,8 +91,12 @@ class RtpHeaderExtensionMap {
   bool IsRegistered(RTPExtensionType type) const;
 
   int32_t GetType(const uint8_t id, RTPExtensionType* type) const;
+  // Return kInvalidType if not found.
+  RTPExtensionType GetType(uint8_t id) const;
 
   int32_t GetId(const RTPExtensionType type, uint8_t* id) const;
+  // Return kInvalidId if not found.
+  uint8_t GetId(RTPExtensionType type) const;
 
   //
   // Methods below ignore any inactive rtp header extensions.