Unify VideoCodecType to/from string functionality

webrtc/common_types.h

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 547 matching lines @@
   kVideoCodecH264,
   kVideoCodecI420,
   kVideoCodecRED,
   kVideoCodecULPFEC,
   kVideoCodecFlexfec,
   kVideoCodecGeneric,
   kVideoCodecUnknown
 };
 
 // Translates from name of codec to codec type and vice versa.
-rtc::Optional<std::string> CodecTypeToPayloadName(VideoCodecType type);
+rtc::Optional<const char*> CodecTypeToPayloadName(VideoCodecType type);
 rtc::Optional<VideoCodecType> PayloadNameToCodecType(const std::string& name);
 
 union VideoCodecUnion {
   VideoCodecVP8 VP8;
   VideoCodecVP9 VP9;
   VideoCodecH264 H264;
 };
 
 // Simulcast is when the same stream is encoded multiple times with different
 // settings such as resolution.
@@ skipping 293 matching lines @@
 enum class RtcpMode { kOff, kCompound, kReducedSize };
 
 enum NetworkState {
   kNetworkUp,
   kNetworkDown,
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_COMMON_TYPES_H_