Revert of RTCRtpReceiver.getContributingSources() added.

content/renderer/media/webrtc/rtc_rtp_contributing_source.h

-// Copyright (c) 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 CONTENT_RENDERER_MEDIA_WEBRTC_RTC_RTP_CONTRIBUTING_SOURCE_H_
-#define CONTENT_RENDERER_MEDIA_WEBRTC_RTC_RTP_CONTRIBUTING_SOURCE_H_
-
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "content/common/content_export.h"
-#include "third_party/WebKit/public/platform/WebRTCRtpContributingSource.h"
-#include "third_party/webrtc/api/rtpreceiverinterface.h"
-
-namespace content {
-
-class CONTENT_EXPORT RTCRtpContributingSource
-    : public blink::WebRTCRtpContributingSource {
- public:
-  explicit RTCRtpContributingSource(const webrtc::RtpSource& source);
-  ~RTCRtpContributingSource() override;
-
-  blink::WebRTCRtpContributingSourceType SourceType() const override;
-  double TimestampMs() const override;
-  uint32_t Source() const override;
-
- private:
-  const webrtc::RtpSource source_;
-
-  DISALLOW_COPY_AND_ASSIGN(RTCRtpContributingSource);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_RENDERER_MEDIA_WEBRTC_RTC_RTP_CONTRIBUTING_SOURCE_H_