Add to-string function for H264 profile level id

webrtc/common_video/h264/profile_level_id.h

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #ifndef WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_
 #define WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_
 
+#include <string>
+
 #include "webrtc/base/optional.h"
 
 namespace webrtc {
 namespace H264 {
 
 enum Profile {
   kProfileConstrainedBaseline,
   kProfileBaseline,
   kProfileMain,
   kProfileConstrainedHigh,
@@ skipping 16 matching lines @@
   kLevel3_2 = 32,
   kLevel4 = 40,
   kLevel4_1 = 41,
   kLevel4_2 = 42,
   kLevel5 = 50,
   kLevel5_1 = 51,
   kLevel5_2 = 52
 };
 
 struct ProfileLevelId {
+  ProfileLevelId() : profile(kProfileBaseline), level(kLevel1) {}

[kthelgason, 2016/11/03 09:39:05]

I'm not convinced that this default constructor is useful.

[magjed_webrtc, 2016/11/03 12:31:16]

Alright, let's remove the default constructor and force explicit initialization.

+  ProfileLevelId(Profile profile, Level level)
+      : profile(profile), level(level) {}
   Profile profile;
   Level level;
 };
 
 // Parse profile level id that is represented as a string of 3 hex bytes.
 // Nothing will be returned if the string is not a recognized H264
 // profile level id.
 rtc::Optional<ProfileLevelId> ParseProfileLevelId(const char* str);
 
+// Returns canonical string representation as three hex bytes of the profile
+// level id, or returns empty string for invalid profile level id.
+std::string ProfileLevelIdToString(const ProfileLevelId& profile_level_id);
+
 }  // namespace H264
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_VIDEO_H264_PROFILE_LEVEL_ID_H_