Reland of Delete class SSRCDatabase, and its global ssrc registry.

webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc

Index: webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc
diff --git a/webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc b/webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc
index 7c7db4dabc7e936a8ad7ee4b6fad16ecba031dbe..b53574c625c3ffdf6a4234ee2eb5ad0bb53d15e6 100644
--- a/webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc
+++ b/webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc
@@ -94,6 +94,8 @@ class RtpRtcpAPITest : public ::testing::Test {
   }
   ~RtpRtcpAPITest() {}
 
+  const uint32_t initial_ssrc = 8888;
+
   void SetUp() override {
     RtpRtcp::Configuration configuration;
     configuration.audio = true;
@@ -101,6 +103,7 @@ class RtpRtcpAPITest : public ::testing::Test {
     configuration.outgoing_transport = &null_transport_;
     configuration.retransmission_rate_limiter = &retransmission_rate_limiter_;
     module_.reset(RtpRtcp::CreateRtpRtcp(configuration));
+    module_->SetSSRC(initial_ssrc);
     rtp_payload_registry_.reset(new RTPPayloadRegistry());
     rtp_receiver_.reset(RtpReceiver::CreateAudioReceiver(
         &fake_clock_, NULL, NULL, rtp_payload_registry_.get()));