Refactor RtpSender and SSRCDatabase a bit.

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
index 7a3133638d7eb20e5e7cefb58e5f9fca027d0ae6..387b3b2df388e1d2ec524a2b20ab9e6f9c7d1bef 100644
--- a/webrtc/modules/rtp_rtcp/source/ssrc_database.h
+++ b/webrtc/modules/rtp_rtcp/source/ssrc_database.h
@@ -13,38 +13,29 @@
 
 #include <set>
 
+#include "webrtc/base/criticalsection.h"
 #include "webrtc/base/random.h"
 #include "webrtc/base/scoped_ptr.h"
-#include "webrtc/system_wrappers/include/static_instance.h"
+#include "webrtc/base/thread_annotations.h"
+#include "webrtc/base/thread_checker.h"
 #include "webrtc/typedefs.h"
 
 namespace webrtc {
-class CriticalSectionWrapper;
 
 class SSRCDatabase {
  public:
-  static SSRCDatabase* GetSSRCDatabase();
-  static void ReturnSSRCDatabase();
+  SSRCDatabase();
+  ~SSRCDatabase();
 
   uint32_t CreateSSRC();
   void RegisterSSRC(uint32_t ssrc);
   void ReturnSSRC(uint32_t ssrc);
 
- protected:
-  SSRCDatabase();
-  virtual ~SSRCDatabase();
-
-  static SSRCDatabase* CreateInstance() { return new SSRCDatabase(); }
-
  private:
-  // Friend function to allow the SSRC destructor to be accessed from the
-  // template class.
-  friend SSRCDatabase* GetStaticInstance<SSRCDatabase>(
-      CountOperation count_operation);
-
-  rtc::scoped_ptr<CriticalSectionWrapper> crit_;
+  rtc::CriticalSection crit_;
   Random random_ GUARDED_BY(crit_);
   std::set<uint32_t> ssrcs_ GUARDED_BY(crit_);
+  rtc::ThreadChecker thread_checker_;
 };
 }  // namespace webrtc