Add interfaces for most major Blimp net components.

blimp/net/stream_socket_connection.h

Index: blimp/net/stream_socket_connection.h
diff --git a/blimp/net/stream_socket_connection.h b/blimp/net/stream_socket_connection.h
index 566cb70b59e13518b133b899f4676c882252392d..9739a09b482e936dc29d9a89faaa0436d1f85e57 100644
--- a/blimp/net/stream_socket_connection.h
+++ b/blimp/net/stream_socket_connection.h
@@ -19,7 +19,8 @@ namespace blimp {
 class StreamSocketConnection : public BlimpConnection {
  public:
   explicit StreamSocketConnection(scoped_ptr<net::StreamSocket> socket);
-  virtual ~StreamSocketConnection();
+
+  ~StreamSocketConnection() override;
 
  private:
   scoped_ptr<net::StreamSocket> socket_;