Add helper functions for negotiating H264 profile level id

webrtc/common_video/h264/profile_level_id.h

Index: webrtc/common_video/h264/profile_level_id.h
diff --git a/webrtc/common_video/h264/profile_level_id.h b/webrtc/common_video/h264/profile_level_id.h
index 44292631cb51212c55d86d598d738d9c276c9c8e..0df75bf9b7e85fbe42642014b24ae3ecad30fbb0 100644
--- a/webrtc/common_video/h264/profile_level_id.h
+++ b/webrtc/common_video/h264/profile_level_id.h
@@ -11,6 +11,7 @@
 #ifndef WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_
 #define WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_
 
+#include <map>
 #include <string>
 
 #include "webrtc/base/optional.h"
@@ -18,6 +19,9 @@
 namespace webrtc {
 namespace H264 {
 
+// Map containting SDP codec parameters.
+typedef std::map<std::string, std::string> CodecParameterMap;
+
 enum Profile {
   kProfileConstrainedBaseline,
   kProfileBaseline,
@@ -60,11 +64,25 @@ struct ProfileLevelId {
 // profile level id.
 rtc::Optional<ProfileLevelId> ParseProfileLevelId(const char* str);
 
+// Parse profile level id that is represented as a string of 3 hex bytes
+// contained in an SDP key-value map. A default profile level id will be
+// returned if the profile-level-id key is missing. Nothing will be returned if
+// the key is present but the string is invalid.
+rtc::Optional<ProfileLevelId> ParseSdpProfileLevelId(
+    const CodecParameterMap& params);
+
 // Returns canonical string representation as three hex bytes of the profile
 // level id, or returns nothing for invalid profile level ids.
 rtc::Optional<std::string> ProfileLevelIdToString(
     const ProfileLevelId& profile_level_id);
 
+// Return negotiated profile level id based on local and remote codec
+// parameters profile-level-id and level-asymmetry-allowed. Return nothing if
+// the parameters are not compatible.
+rtc::Optional<ProfileLevelId> NegotiateProfileLevelId(
+    const CodecParameterMap& local_params,
+    const CodecParameterMap& remote_params);
+
 }  // namespace H264
 }  // namespace webrtc