Implemented the GetSources() in native code.

webrtc/api/rtpparameters.h

 /*
  *  Copyright 2015 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 49 matching lines @@
   GENERIC_NACK,
   PLI,  // Usable with NACK.
   FIR,  // Usable with CCM.
 };
 
 enum class DtxStatus {
   DISABLED,
   ENABLED,
 };
 
-enum class DegradationPreference {

[Zhi Huang, 2017/03/31 06:44:05]

This is changed because it accidentally conflict with a name in the video
encoder part.

[Taylor Brandstetter, 2017/03/31 22:10:50]

It looks like the two enums are referring to the same thing. Could they just be
unified? May be better in a standalone CL.

+enum class RtpDegradationPreference {
   MAINTAIN_FRAMERATE,
   MAINTAIN_RESOLUTION,
   BALANCED,
 };
 
 enum class PriorityType { VERY_LOW, LOW, MEDIUM, HIGH };
 
 struct RtcpFeedback {
   RtcpFeedbackType type = RtcpFeedbackType::CCM;
 
@@ skipping 353 matching lines @@
   std::string mid;
 
   std::vector<RtpCodecParameters> codecs;
 
   // TODO(deadbeef): Not implemented with PeerConnection senders/receivers.
   std::vector<RtpHeaderExtensionParameters> header_extensions;
 
   std::vector<RtpEncodingParameters> encodings;
 
   // TODO(deadbeef): Not implemented.
-  DegradationPreference degradation_preference =
-      DegradationPreference::BALANCED;
+  RtpDegradationPreference degradation_preference =
+      RtpDegradationPreference::BALANCED;
 
   bool operator==(const RtpParameters& o) const {
     return mid == o.mid && codecs == o.codecs &&
            header_extensions == o.header_extensions &&
            encodings == o.encodings &&
            degradation_preference == o.degradation_preference;
   }
   bool operator!=(const RtpParameters& o) const { return !(*this == o); }
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_RTPPARAMETERS_H_