Revert "RtpTransceiverInterface: introduce SetOfferedRtpHeaderExtensions."

This reverts commit 71db9acc4019b8c9c13b14e6a022cbb3b4255b09.

Reason for revert: breaks downstream project.
Reason for force push: win bot broken.

Original change's description:
> RtpTransceiverInterface: introduce SetOfferedRtpHeaderExtensions.
>
> This change adds exposure of a new transceiver method for
> modifying the extensions offered in the next SDP negotiation,
> following spec details in https://w3c.github.io/webrtc-extensions/#rtcrtptransceiver-interface.
>
> Features:
> - The interface allows to control the negotiated direction as
>   per https://tools.ietf.org/html/rfc5285#page-7.
> - The interface allows to remove an extension from SDP
>   negotiation by modifying the direction to
>   RtpTransceiverDirection::kStopped.
>
> Note: support for signalling directionality of header extensions
> in the SDP isn't implemented yet.
>
> https://chromestatus.com/feature/5680189201711104.
> Intent to prototype: https://groups.google.com/a/chromium.org/g/blink-dev/c/65YdUi02yZk
>
> Bug: chromium:1051821
> Change-Id: Iaabc34446f038c46d93c442e90c2a77f77d542d4
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176408
> Reviewed-by: Harald Alvestrand <hta@webrtc.org>
> Commit-Queue: Markus Handell <handellm@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31487}

TBR=hta@webrtc.org,handellm@webrtc.org

# Not skipping CQ checks because original CL landed > 1 day ago.

No-Try: true
Bug: chromium:1051821
Change-Id: I70e1a07225d7eeec7480fa5577d8ff647eba6902
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/177103
Commit-Queue: Markus Handell <handellm@webrtc.org>
Reviewed-by: Markus Handell <handellm@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31516}
diff --git a/pc/rtp_transceiver.h b/pc/rtp_transceiver.h
index be46ccf..0668447 100644
--- a/pc/rtp_transceiver.h
+++ b/pc/rtp_transceiver.h
@@ -195,9 +195,6 @@
   }
   std::vector<RtpHeaderExtensionCapability> HeaderExtensionsToOffer()
       const override;
-  RTCError SetOfferedRtpHeaderExtensions(
-      rtc::ArrayView<const RtpHeaderExtensionCapability>
-          header_extensions_to_offer) override;
 
  private:
   void OnFirstPacketReceived(cricket::ChannelInterface* channel);
@@ -223,7 +220,7 @@
   cricket::ChannelInterface* channel_ = nullptr;
   cricket::ChannelManager* channel_manager_ = nullptr;
   std::vector<RtpCodecCapability> codec_preferences_;
-  std::vector<RtpHeaderExtensionCapability> header_extensions_to_offer_;
+  std::vector<RtpHeaderExtensionCapability> HeaderExtensionsToOffer_;
 };
 
 BEGIN_SIGNALING_PROXY_MAP(RtpTransceiver)
@@ -244,9 +241,6 @@
 PROXY_CONSTMETHOD0(std::vector<RtpCodecCapability>, codec_preferences)
 PROXY_CONSTMETHOD0(std::vector<RtpHeaderExtensionCapability>,
                    HeaderExtensionsToOffer)
-PROXY_METHOD1(webrtc::RTCError,
-              SetOfferedRtpHeaderExtensions,
-              rtc::ArrayView<const RtpHeaderExtensionCapability>)
 END_PROXY_MAP()
 
 }  // namespace webrtc