Revert "Revert of Parse FlexFEC RTP headers in Call and add integration with BWE. (patchset #17 id:460001 of https://codereview.webrtc.org/2553863003/ )"

Problem fixed: RTP header extensions were not properly set in tests.

BUG=webrtc:5654

Review-Url: https://codereview.webrtc.org/2593963003
Cr-Commit-Position: refs/heads/master@{#15741}

webrtc/modules/rtp_rtcp/source/rtp_packet.cc

@@ -86,6 +86,10 @@ bool Packet::Parse(const uint8_t* buffer, size_t buffer_size) {
   return true;
 }
 
+bool Packet::Parse(rtc::ArrayView<const uint8_t> packet) {
+  return Parse(packet.data(), packet.size());
+}
+
 bool Packet::Parse(rtc::CopyOnWriteBuffer buffer) {
   if (!ParseBuffer(buffer.cdata(), buffer.size())) {
     Clear();