Reland of TCRtpReceiver.getContributingSources() added.

third_party/WebKit/Source/modules/peerconnection/RTCRtpContributingSource.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/RTCRtpContributingSource.h"
+
+#include "modules/peerconnection/RTCRtpReceiver.h"
+#include "public/platform/WebRTCRtpContributingSource.h"
+
+namespace blink {
+
+RTCRtpContributingSource::RTCRtpContributingSource(
+    RTCRtpReceiver* receiver,
+    const WebRTCRtpContributingSource& webContributingSource)
+    : receiver_(receiver),
+      timestamp_ms_(webContributingSource.TimestampMs()),
+      source_(webContributingSource.Source()) {
+  DCHECK(receiver_);
+}
+
+void RTCRtpContributingSource::UpdateMembers(
+    const WebRTCRtpContributingSource& webContributingSource) {
+  timestamp_ms_ = webContributingSource.TimestampMs();
+  DCHECK_EQ(webContributingSource.Source(), source_);
+}
+
+double RTCRtpContributingSource::timestamp() {
+  receiver_->UpdateSourcesIfNeeded();
+  return timestamp_ms_;
+}
+
+uint32_t RTCRtpContributingSource::source() const {
+  // Skip |receiver_->UpdateSourcesIfNeeded()|, |source_| is a constant.
+  return source_;
+}
+
+DEFINE_TRACE(RTCRtpContributingSource) {
+  visitor->Trace(receiver_);
+}
+
+}  // namespace blink