Reland of TCRtpReceiver.getContributingSources() added.

third_party/WebKit/Source/modules/peerconnection/RTCRtpReceiver.h

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef RTCRtpReceiver_h
 #define RTCRtpReceiver_h
 
+#include <map>
+
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/mediastream/MediaStreamTrack.h"
+#include "modules/peerconnection/RTCRtpContributingSource.h"
 #include "platform/heap/GarbageCollected.h"
 #include "platform/heap/Member.h"
 #include "platform/heap/Visitor.h"
 #include "public/platform/WebRTCRtpReceiver.h"
 
 namespace blink {
 
 // https://w3c.github.io/webrtc-pc/#rtcrtpreceiver-interface
 class RTCRtpReceiver final : public GarbageCollectedFinalized<RTCRtpReceiver>,
                              public ScriptWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
   // Takes ownership of the receiver.
   RTCRtpReceiver(std::unique_ptr<WebRTCRtpReceiver>, MediaStreamTrack*);
 
   MediaStreamTrack* track() const;
+  const HeapVector<Member<RTCRtpContributingSource>>& getContributingSources();
+
+  void UpdateSourcesIfNeeded();
 
   DECLARE_VIRTUAL_TRACE();
 
  private:
+  void SetContributingSourcesNeedsUpdating();
+
   std::unique_ptr<WebRTCRtpReceiver> receiver_;
   Member<MediaStreamTrack> track_;
+
+  // All contributing sources that have ever been returned by
+  // |getContributingSources| that are still alive. If |UpdateSourcesIfNeeded|
+  // encounters a source that already has an associate
+  // |RTCRtpContributingSource| it will be kept up-to-date. Garbage collected
+  // sources are automatically removed from the map.
+  HeapHashMap<uint32_t,
+              WeakMember<RTCRtpContributingSource>,
+              typename DefaultHash<uint32_t>::Hash,
+              WTF::UnsignedWithZeroKeyHashTraits<uint32_t>>
+      contributing_sources_by_source_id_;
+  // The current contributing sources (|getContributingSources|).
+  HeapVector<Member<RTCRtpContributingSource>> contributing_sources_;
+  bool contributing_sources_needs_updating_ = true;
 };
 
 }  // namespace blink
 
 #endif  // RTCRtpReceiver_h