Style cleanups in rtp header extension traits:

webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
index 0d4ce95c6b452fa875091636f624a826b135f56a..1356069ca9c138d6288819ac7f2200563afc7443 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
@@ -31,11 +31,10 @@ namespace webrtc {
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=2 |              absolute send time               |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-const char* AbsoluteSendTime::kName =
+constexpr RTPExtensionType AbsoluteSendTime::kId;
+constexpr uint8_t AbsoluteSendTime::kValueSizeBytes;

[brandtr, 2016/10/28 13:26:56]

Are the declarations above just for documentation, or do they have a specific
use?

[danilchap, 2016/10/28 13:32:03]

presence of these declaration allows to use constants in RTC_DCHECK_EQ macros
and any other place where address of the kId can be taken.

+const char* const AbsoluteSendTime::kUri =
     "http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time";
-bool AbsoluteSendTime::IsSupportedFor(MediaType type) {
-  return true;
-}
 
 bool AbsoluteSendTime::Parse(const uint8_t* data, uint32_t* time_24bits) {
   *time_24bits = ByteReader<uint32_t, 3>::ReadBigEndian(data);
@@ -59,19 +58,10 @@ bool AbsoluteSendTime::Write(uint8_t* data, int64_t time_ms) {
 //   |  ID   | len=0 |V|   level     |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //
-const char* AudioLevel::kName = "urn:ietf:params:rtp-hdrext:ssrc-audio-level";
-bool AudioLevel::IsSupportedFor(MediaType type) {
-  switch (type) {
-    case MediaType::ANY:
-    case MediaType::AUDIO:
-      return true;
-    case MediaType::VIDEO:
-    case MediaType::DATA:
-      return false;
-  }
-  RTC_NOTREACHED();
-  return false;
-}
+constexpr RTPExtensionType AudioLevel::kId;
+constexpr uint8_t AudioLevel::kValueSizeBytes;

[brandtr, 2016/10/28 13:26:56]

Same here, and below.

+const char* const AudioLevel::kUri =
+    "urn:ietf:params:rtp-hdrext:ssrc-audio-level";
 
 bool AudioLevel::Parse(const uint8_t* data,
                        bool* voice_activity,
@@ -105,19 +95,10 @@ bool AudioLevel::Write(uint8_t* data,
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=2 |              transmission offset              |
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-const char* TransmissionOffset::kName = "urn:ietf:params:rtp-hdrext:toffset";
-bool TransmissionOffset::IsSupportedFor(MediaType type) {
-  switch (type) {
-    case MediaType::ANY:
-    case MediaType::VIDEO:
-      return true;
-    case MediaType::AUDIO:
-    case MediaType::DATA:
-      return false;
-  }
-  RTC_NOTREACHED();
-  return false;
-}
+constexpr RTPExtensionType TransmissionOffset::kId;
+constexpr uint8_t TransmissionOffset::kValueSizeBytes;
+const char* const TransmissionOffset::kUri =
+    "urn:ietf:params:rtp-hdrext:toffset";
 
 bool TransmissionOffset::Parse(const uint8_t* data, int32_t* rtp_time) {
   *rtp_time = ByteReader<int32_t, 3>::ReadBigEndian(data);
@@ -135,11 +116,10 @@ bool TransmissionOffset::Write(uint8_t* data, int32_t rtp_time) {
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //  |  ID   | L=1   |transport wide sequence number |
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-const char* TransportSequenceNumber::kName =
+constexpr RTPExtensionType TransportSequenceNumber::kId;
+constexpr uint8_t TransportSequenceNumber::kValueSizeBytes;
+const char* const TransportSequenceNumber::kUri =
     "http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions";
-bool TransportSequenceNumber::IsSupportedFor(MediaType type) {
-  return true;
-}
 
 bool TransportSequenceNumber::Parse(const uint8_t* data, uint16_t* value) {
   *value = ByteReader<uint16_t>::ReadBigEndian(data);
@@ -162,19 +142,9 @@ bool TransportSequenceNumber::Write(uint8_t* data, uint16_t value) {
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 //   |  ID   | len=0 |0 0 0 0 C F R R|
 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
-const char* VideoOrientation::kName = "urn:3gpp:video-orientation";
-bool VideoOrientation::IsSupportedFor(MediaType type) {
-  switch (type) {
-    case MediaType::ANY:
-    case MediaType::VIDEO:
-      return true;
-    case MediaType::AUDIO:
-    case MediaType::DATA:
-      return false;
-  }
-  RTC_NOTREACHED();
-  return false;
-}
+constexpr RTPExtensionType VideoOrientation::kId;
+constexpr uint8_t VideoOrientation::kValueSizeBytes;
+const char* const VideoOrientation::kUri = "urn:3gpp:video-orientation";
 
 bool VideoOrientation::Parse(const uint8_t* data, VideoRotation* rotation) {
   *rotation = ConvertCVOByteToVideoRotation(data[0]);
@@ -203,20 +173,8 @@ bool VideoOrientation::Write(uint8_t* data, uint8_t value) {
 //  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 constexpr RTPExtensionType PlayoutDelayLimits::kId;
 constexpr uint8_t PlayoutDelayLimits::kValueSizeBytes;
-const char* PlayoutDelayLimits::kName =
+const char* const PlayoutDelayLimits::kUri =
     "http://www.webrtc.org/experiments/rtp-hdrext/playout-delay";
-bool PlayoutDelayLimits::IsSupportedFor(MediaType type) {
-  switch (type) {
-    case MediaType::ANY:
-    case MediaType::VIDEO:
-      return true;
-    case MediaType::AUDIO:
-    case MediaType::DATA:
-      return false;
-  }
-  RTC_NOTREACHED();
-  return false;
-}
 
 bool PlayoutDelayLimits::Parse(const uint8_t* data,
                                PlayoutDelay* playout_delay) {