Reland of TCRtpReceiver.getContributingSources() added.

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

 // 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.
 
 #include "modules/peerconnection/RTCRtpReceiver.h"
 
+#include "bindings/core/v8/Microtask.h"
+#include "public/platform/WebRTCRtpContributingSource.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 RTCRtpReceiver::RTCRtpReceiver(std::unique_ptr<WebRTCRtpReceiver> receiver,
                                MediaStreamTrack* track)
     : receiver_(std::move(receiver)), track_(track) {
   DCHECK(receiver_);
   DCHECK(track_);
   DCHECK_EQ(static_cast<String>(receiver_->Track().Id()), track_->id());
 }
 
 MediaStreamTrack* RTCRtpReceiver::track() const {
   return track_;
 }
 
+const HeapVector<Member<RTCRtpContributingSource>>&
+RTCRtpReceiver::getContributingSources() {
+  UpdateSourcesIfNeeded();
+  return contributing_sources_;
+}
+
+void RTCRtpReceiver::UpdateSourcesIfNeeded() {
+  if (!contributing_sources_needs_updating_)
+    return;
+  contributing_sources_.Clear();
+  for (const std::unique_ptr<WebRTCRtpContributingSource>&
+           web_contributing_source : receiver_->GetSources()) {
+    if (web_contributing_source->SourceType() ==
+        WebRTCRtpContributingSourceType::SSRC) {
+      // TODO(hbos): When |getSynchronizationSources| is added to get SSRC
+      // sources don't ignore SSRCs here.
+      continue;
+    }
+    DCHECK_EQ(web_contributing_source->SourceType(),
+              WebRTCRtpContributingSourceType::CSRC);
+    auto it = contributing_sources_by_source_id_.Find(
+        web_contributing_source->Source());
+    if (it == contributing_sources_by_source_id_.end()) {
+      RTCRtpContributingSource* contributing_source =
+          new RTCRtpContributingSource(this, *web_contributing_source);
+      contributing_sources_by_source_id_.insert(contributing_source->source(),
+                                                contributing_source);
+      contributing_sources_.push_back(contributing_source);
+    } else {
+      it->value->UpdateMembers(*web_contributing_source);
+      contributing_sources_.push_back(it->value);
+    }
+  }
+  // Clear the flag and schedule a microtask to reset it to true. This makes
+  // the cache valid until the next microtask checkpoint. As such, sources
+  // represent a snapshot and can be compared reliably in .js code, no risk of
+  // being updated due to an RTP packet arriving. E.g.
+  // "source.timestamp == source.timestamp" will always be true.
+  contributing_sources_needs_updating_ = false;
+  Microtask::EnqueueMicrotask(
+      WTF::Bind(&RTCRtpReceiver::SetContributingSourcesNeedsUpdating,
+                WrapWeakPersistent(this)));
+}
+
+void RTCRtpReceiver::SetContributingSourcesNeedsUpdating() {
+  contributing_sources_needs_updating_ = true;
+}
+
 DEFINE_TRACE(RTCRtpReceiver) {
   visitor->Trace(track_);
+  visitor->Trace(contributing_sources_by_source_id_);
+  visitor->Trace(contributing_sources_);
 }
 
 }  // namespace blink