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

webrtc/voice_engine/channel_manager.h

Index: webrtc/voice_engine/channel_manager.h
diff --git a/webrtc/voice_engine/channel_manager.h b/webrtc/voice_engine/channel_manager.h
index 65cf9942d1b0afe056e489a40cd048eb750e326e..ae16aca2b878aa8c6782c72294dd924abb8596e6 100644
--- a/webrtc/voice_engine/channel_manager.h
+++ b/webrtc/voice_engine/channel_manager.h
@@ -16,7 +16,6 @@
 
 #include "webrtc/base/constructormagic.h"
 #include "webrtc/base/criticalsection.h"
-#include "webrtc/base/random.h"
 #include "webrtc/base/scoped_ref_ptr.h"
 #include "webrtc/system_wrappers/include/atomic32.h"
 #include "webrtc/typedefs.h"
@@ -117,9 +116,6 @@
   rtc::CriticalSection lock_;
   std::vector<ChannelOwner> channels_;
 
-  // For generation of random ssrc:s.
-  webrtc::Random random_;
-
   RTC_DISALLOW_COPY_AND_ASSIGN(ChannelManager);
 };
 }  // namespace voe