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

webrtc/modules/rtp_rtcp/source/ssrc_database.h

Index: webrtc/modules/rtp_rtcp/source/ssrc_database.h
diff --git a/webrtc/modules/rtp_rtcp/source/ssrc_database.h b/webrtc/modules/rtp_rtcp/source/ssrc_database.h
new file mode 100644
index 0000000000000000000000000000000000000000..2f6357aec061022a3b5328a11168b4bac79ee93b
--- /dev/null
+++ b/webrtc/modules/rtp_rtcp/source/ssrc_database.h
@@ -0,0 +1,62 @@
+/*
+ *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_SSRC_DATABASE_H_
+#define WEBRTC_MODULES_RTP_RTCP_SOURCE_SSRC_DATABASE_H_
+
+#include <set>
+
+#include "webrtc/base/criticalsection.h"
+#include "webrtc/base/random.h"
+#include "webrtc/base/thread_annotations.h"
+#include "webrtc/system_wrappers/include/static_instance.h"
+#include "webrtc/typedefs.h"
+
+namespace webrtc {
+
+// TODO(tommi, holmer): Look into whether we can eliminate locking in this
+// class or the class itself completely once voice engine doesn't rely on it.
+// At the moment voe_auto_test requires locking, but it's not clear if that's
+// an issue with the test code or if it reflects real world usage or if that's
+// the best design performance wise.
+// If we do decide to keep the class, we should at least get rid of using
+// StaticInstance.
+class SSRCDatabase {
+ public:
+  static SSRCDatabase* GetSSRCDatabase();
+  static void ReturnSSRCDatabase();
+
+  uint32_t CreateSSRC();
+  void RegisterSSRC(uint32_t ssrc);
+  void ReturnSSRC(uint32_t ssrc);
+
+ protected:
+  SSRCDatabase();
+  ~SSRCDatabase();
+
+  static SSRCDatabase* CreateInstance() { return new SSRCDatabase(); }
+
+  // Friend function to allow the SSRC destructor to be accessed from the
+  // template class.
+  friend SSRCDatabase* GetStaticInstance<SSRCDatabase>(
+      CountOperation count_operation);
+
+ private:
+  rtc::CriticalSection crit_;
+  Random random_ GUARDED_BY(crit_);
+  std::set<uint32_t> ssrcs_ GUARDED_BY(crit_);
+  // TODO(tommi): Use a thread checker to ensure the object is created and
+  // deleted on the same thread.  At the moment this isn't possible due to
+  // voe::ChannelOwner in voice engine.  To reproduce, run:
+  // voe_auto_test --automated --gtest_filter=*MixManyChannelsForStressOpus
+};
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_SSRC_DATABASE_H_