Only initialize usrsctp when it's used and uninitialize when it's not being used.

webrtc/media/sctp/sctpdataengine.h

Index: webrtc/media/sctp/sctpdataengine.h
diff --git a/webrtc/media/sctp/sctpdataengine.h b/webrtc/media/sctp/sctpdataengine.h
index 8eb99564ca23d7fbacbe72d71e326e464c74a3f8..f9a3b5a6547e00dacbffafab6b0404311e608eb9 100644
--- a/webrtc/media/sctp/sctpdataengine.h
+++ b/webrtc/media/sctp/sctpdataengine.h
@@ -25,6 +25,7 @@ enum PreservedErrno {
 }  // namespace cricket
 
 #include "webrtc/base/copyonwritebuffer.h"
+#include "webrtc/base/gtest_prod_util.h"
 #include "webrtc/media/base/codec.h"
 #include "webrtc/media/base/mediachannel.h"
 #include "webrtc/media/base/mediaengine.h"
@@ -75,19 +76,13 @@ class SctpDataMediaChannel;
 class SctpDataEngine : public DataEngineInterface, public sigslot::has_slots<> {
  public:
   SctpDataEngine();
-  virtual ~SctpDataEngine();
+  ~SctpDataEngine() override;
 
-  virtual DataMediaChannel* CreateChannel(DataChannelType data_channel_type);
-
-  virtual const std::vector<DataCodec>& data_codecs() { return codecs_; }
-
-  static int SendThresholdCallback(struct socket* sock, uint32_t sb_free);
+  DataMediaChannel* CreateChannel(DataChannelType data_channel_type) override;
+  const std::vector<DataCodec>& data_codecs() override { return codecs_; }
 
  private:
-  static int usrsctp_engines_count;
-  std::vector<DataCodec> codecs_;
-
-  static SctpDataMediaChannel* GetChannelFromSocket(struct socket* sock);
+  const std::vector<DataCodec> codecs_;
 };
 
 // TODO(ldixon): Make into a special type of TypedMessageData.
@@ -161,11 +156,16 @@ class SctpDataMediaChannel : public DataMediaChannel,
 
   void OnSendThresholdCallback();
   // Helper for debugging.
-  void set_debug_name(const std::string& debug_name) {
+  void set_debug_name_for_testing(const char* debug_name) {
     debug_name_ = debug_name;
   }
-  const std::string& debug_name() const { return debug_name_; }
   const struct socket* socket() const { return sock_; }
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(SctpDataMediaChannelTest, EngineSignalsRightChannel);
+  static int SendThresholdCallback(struct socket* sock, uint32_t sb_free);
+  static SctpDataMediaChannel* GetChannelFromSocket(struct socket* sock);
+
  private:
   sockaddr_conn GetSctpSockAddr(int port);
 
@@ -229,8 +229,8 @@ class SctpDataMediaChannel : public DataMediaChannel,
   StreamSet queued_reset_streams_;
   StreamSet sent_reset_streams_;
 
-  // A human-readable name for debugging messages.
-  std::string debug_name_;
+  // A static human-readable name for debugging messages.
+  const char* debug_name_;
 };
 
 }  // namespace cricket